REESE    LIBRARY 

OF    THK 

V 

UNIVERSITY   OF   CALIFORNIA. 


Received. J 

Accessions  No.  .2/£6>4-__         Shelf  No. . 

J 


V-         OF    THE 

UNIVERSITY 


FRONTISPIECE. 


FIG.  i. 

THE  PHENOMENON  OF  "  BARKING,"  AS  MANIFESTED  BY  IRONS  F  AND  Fx.     (See  Page  36.) 


FlG.    2. 

DIFFERENCE   IN   APPEARANCE   OF   FRACTURES  PRODUCED   BY   IMPACT,  OF  VARYING   DEGREES   OF 
ENERGY,  THE   MATERIAL  BEING  THE  SAME.     (See  Page  35.) 


Udiotype  Printing  CV  Boston. 


JBIVEHSITY 


BEARDSLEE  ON  WROUGHT-IRON  AND  CHAM-CABLES. 

EXPERIMENTS 

ON  THE 

STBENGTH  OF  WKOUGHT-IRON 

AND  OF 

CHAIN-CABLES. 


REPORT  OF  THE  COMMITTEES  OF  THE  UNITED  STATES  BOARD 

APPOINTED  TO  TEST  IRON,  STEEL  AND  OTHER  METALS, 

ON  CHAIN-CABLES,  MALLEABLE  IRON,  AND 

RE-HEATING  AND  RE-ROLLING 

WROUGHT-IRON; 

INCLUDING 

MISCELLANEOUS  INVESTIGATIONS  INTO  THE  PHYSICAL 

AND  CHEMICAL  PROPERTIES  OF  ROLLED 

WROUGHT-IRON. 


BY 

COMMANDER  L.  A.  BEARDSLEE,  U.S.N., 

Member  of  the  Board,  and  Chairman  of  the  Committees. 

anfc 


WILLIAM  KENT,  M.E., 

Formerly  Assistant  to  the  Committee  on  Alloys  of  the  United  States  Board; 

Associate  Editor  of  the  "American  Mamifacturer  and 

Iron  World,"  Pittsburgh,  Penn. 


NEW  YORK: 

JOHN    WILEY    AND    SONS, 

15   ASTOR   PLACE. 

1879. 


COPTRIGHT,  1879, 

BY  WILLIAM  KENT. 


PREFACE. 


THE  Report  of  which  the  following  pages  are  an  abridgment  was 
published  by  the  United  States  Government  in  1879,  as  part  of 
Executive  Document  No.  98,  House  of  Representatives,  Forty-fifth 
Congress,  Second  Session. 

It  forms  an  octavo  of  two  hundred  and  sixty-seven  pages,  with 
thirteen  heliotype-plates,  and  several  wood-cuts.  It  is  not  only  by 
far  the  most  elaborate  record  of  tests  of  wrought-iron  and  of  chain- 
cables  that  has  ever  been  given  to  the  world,  but  it  is  the  most 
valuable  in  results;  in  describing  newly  observed  phenomena,  in 
tabulating  variations  of  strength  due  to  differences  in  methods  of 
manufacture,  and  revealing  their  causes,  in  investigation  of  the  effect 
of  impact,  in  pointing  out  causes  of  defects  in  strength  of  both 
bars  and  cables,  and  generally  in  giving  information  that  is  of  imme- 
diate practical  value  to  manufacturers  of  iron  and  to  engineers. 

As  but  a  limited  number  of  copies  of  the  report  were  issued  by  the 
Government,  and  as  it  contains  a  large  amount  of  detailed  tabular 
matter,  which,  while  necessary  in  an  official  report  of  this  kind,  to 
corroborate  the  conclusions  deduced, *is  not  necessary  to  a  full  com- 
prehension of  these  conclusions,  —  it  has  been  thought  that  an 
abridgment  would  be  acceptable  to  many  who  would  be  unable  to 
obtain  the  original  work. 

The  undersigned,  in  preparing  the  abridgment,  has  had  the  full 
consent  of  Commander  Beardslee,  and  obtained  his  approval  of 

the  manuscript  prior  to  publication. 

WM.  KENT. 
PITTSBURGH,  PEKN\,  May,  1879. 


CONTENTS. 


SECTION  I. 

PAGE 

INTRODUCTION 1 

THE  BAB. —  PART  1 4 

Testing-Machines,  and  Methods  of  Testing 5 

Notes  upon  the  "Records  of  Bars  tested  by  Tension"  ...  6 

Strength  and  Elastic  Limit  of  Round  Bar-Iron      ....  8 

THE  BAR.— PART  II 11 

Investigation    of   the  Effect  of  Differences  in   the  Amount  of 

Reduction  by  the  Rolls 11 

SECTION  II. 

PART  I.  —  PROPER  FORM  AND  PROPORTIONS  OF  TEST-PIECES       .        .      20 
PART  II.  —  COMPARATIVE   STRENGTH   OF   BARS   IN   THEIR  NORMAL 
CONDITION,  AND  AS  REDUCED  BY  TURNING  AWAY  THE  SKIN  AND 
ADJACENT  IRON 27 

SECTION  III. 

TESTS  OF  BARS  BY  IMPACT  ;  SHOWING  ACTION  OF  VARIOUS  TYPES  OF 

IRON  UNDER  SUDDEN  STRAINS     ........  31 

Method  of  testing  by  Impact   .        . 32 

Barking 36 

Crystallization 30 

Record  of  Impact  Tests •     .  37 

SECTION  IV. 

A  PAPER  DESCRIBING  A  SERIES  OF  EXPERIMENTS  TO  DETERMINE 
FACTS  IN  REGARD  TO  THE  OPERATION  OF  THE  LAW  CALLED  THE 
ELEVATION  OF  THE  LIMIT  OF  STRESS  .  .  40 


VI  CONTENTS. 


SECTION  V. 

THE  CABLE 49 

Experiments  upon  Comparative  Strength  of  Studded  and  Unstud- 

ded  Links 52 

Description  of  Method  of  testing  Cables 54 

Weight  of  Chain-Cables 57 

Methods  by  which  the  Weight  of  Chain-Cables  can  be  reduced 

in  a  greater  Ratio  than  the  Strength 58 

Comparison  of  Results  obtained  by  Tension  upon  Sections  of 
Cable-Links,  and  upon  Bars  of  the  Iron  from  which  Links  were 
made 62 

SECTION  VI. 

PROOF-STRAINS  FOR  CHAIN-CABLES 68 

Effects  of  the  Use  of  Strains  prescribed  by  the  Admiralty  Proof- 
Table  68 

Discussion  of  the  Principles  upon  which  Proof-Strains  should  be 

based 71 

Ratio  of  Strength  of  Sections  of  Links  to  that  of  the  Bars  from 

which  they  were  made 72 

Probable  Strength  of  Round  Bars,  calculated  with  an  Allowance 

for  Variation  in  Strength  due  to  Variation  in  Diameter  .  .  77 
Probable  Strength  of  Cables  made  from  Bars  of  given  Strength  .  79 

Recommended  Proof -Table 81 

Comparison  of  the  Proof-Strains  recommended,  and  the  Strains 
in  Use  . 81 

SECTION  VII. 

PART  I.  —  NOTES  UPON  THE  IRONS  EXAMINED  .  .  .  .83 

PART  II.  —  COMPARISON  OF  CHEMICAL  AND  PHYSICAL  RESULTS  .  .  92 

Analyses  of  the  Irons  use/1  in  making  Chain-Cables  ...  93 
Relative  Values  of  Iron  in  Bars,  in  Tenacity,  Reduction  of  Area, 

and  Elongation,  and  in  Proportion  of  Chain  to  Bar  ...  95 
Summary  of  the  Principal  Physical  and  Chemical  Properties  of 

Sixteen  Irons  .  .  ^ .  9(5 

Effects  of  Phosphorus  .  % .97 

Effects  of  Silicon  . 101 

Effects  of  Carbon 102 

Effects  of  Manganese,  Copper,  Nickel,  Cobalt,  Sulphur,  and  Slag,  105 

Welding ' 106 

What  is  learned  from  Chemical  Analyses 113 

Conclusions  derived  from  a  Comparison  of  Chemical  and  Physical 

Results    .                                                                         ...  117 


UNIVERSITY 


REPORT 


RESULTS  Or  INVESTIGATIONS  MADE  BY  COMMITTEES  D,  I,  AND 

M,  OF  THE  UNITED-STATES  BOAED  APPOINTED  TO 

TEST  IRON,  STEEL,  AND  OTHER  METALS. 


SECTION  I. 
INTRODUCTION. 

THE  investigations  assigned  to  the  three  committees  desig- 
nated by  the  letters  D,  H,  and  M  were  as  follows :  — 

To  Committee  D,  "  On  Chain  and  Wire  Ropes,"  with  instruc- 
tions "  to  determine  the  character  of  iron  best  adapted  for 
chain  cables,  the  best  form  and  proportions  of  link,  and  the 
qualities  of  metal  used  in  the  manufacture  of  iron  and  steel 
wire  rope." 

To  Committee  H,  "On  Iron,  Malleable,"  with  instructions  "to 
examine  and  report  upon  the  mechanical  and  physical  proper- 
ties of  wrought-iron." 

To  Committee  M,  "  On  Re-heating  and  Re-rolling,"  with  in- 
structions "  to  examine  and  report  upon  the  effects  of  re-heat- 
ing and  re-rolling,  or  otherwise  re-working,  of  hammering  as 
compared  with  rolling,  and  of  annealing  the  metals." 

The  work  thus  assigned  to  three  different  committees  was 
of  such  a  nature,  that  experiments  made  by  any  one  of  them 
would  necessarily  furnish  data  which  would  prove  of  value  to 


2  WROUGHT-IKON  AND  CHAIN-CABLES. 

all ;  and  as  the  three  committees  consisted  of  but  five  members 
of  the  board,  one  of  whom  was  chairman  of  all,  it  was  consid- 
ered advisable,  in  order  to  economize  time,  labor,  and  means 
by  the  avoidance  of  duplication  of  expensive  experiments,  and 
of  making  duplicate  and  triplicate  reports  of  the  same  series, 
to  consolidate  the  committees,  and  to  conduct  the  investigations 
in  such  a  manner  that  a  single  report  would  cover  the  whole 
ground.  In  thus  concentrating  the  work,  it  was  necessary  that 
a  leading  object  should  be  selected,  and  it  was  considered  that 
the  research  required  to  establish  the  characteristics  of  iron 
best  adapted  for  the  manufacture  of  cables  would  furnish  data 
which  would  bear  more  or  less  upon  the  subjects  to  be  investi- 
gated by  Committees  H  and  M ;  while  it  would  be  quite  practi- 
cable to  select  from  the  wide  field  presented  by  "wrought- 
iron,"  and  differences  in  methods  of  treating  it,  any  number 
of  lines  of  research,  none  of  which  would  prove  of  much  ser- 
vice in  establishing  points  in  regard  to  chain-iron. 

Our  experiments,  therefore,  have  been  all  so  carried  out,  that 
while  we  have  been  able  to  obtain  data,  both  as  to  the  mechan- 
ical and  physical  properties  of  wrought-iron,  and  as  to  the 
effects  of  different  methods  of  treatment  of  the  raw  material, 
all  have  been  made  to  contribute  their  quota  toward  the  estab- 
lishment of  methods  by  which  an  iron  could  be  judged  cor- 
rectly as  to  its  adaptability  for  chain-cable  manufacture.  Such 
points  well  established  would  prove  to  possess  value,  not  only 
to  the  manufacturers  and  purchasers  of  cables  and  cable-iron, 
but  also  to  manufacturers  of  iron  bridges  and  other  construc- 
tions, which,  like  the  cable,  depend  for  their  value  upon  their 
power  of  resisting  to  the  utmost  destroying  forces  of  various 
and  irregular  natures! 

In  submitting  this  report,  we  would  say  that  the  extent  of 
our  investigations  has  been  restricted  by  narrowness  of  our 
means,  and  the  necessity  which  has  arisen  that  we  should  sub- 
mit the  results  of  such  work  as  we  have  accomplished.  They 
but  point  the  way  toward  a  thorough  re-examination  of  the 
subjects  involved,  which,  based  upon  our  results,  would  provide 


INTRODUCTION.  3 

a  valuable  mass  of  information,  to  which  this  report  would 
occupy  the  relation  of  a  preface. 

The  cable-link  is  but  a  modification  of  the  round  rolled  bar, 
and  its  qualities  must  depend  upon  those  of  the  bar  from  which 
it  is  made.  Therefore  we  have  selected  the  ROUND  BAR  as  the 
foundation  of  our  work ;  and  our  endeavor  has  been  to  ascertain 
what  qualities  should  be  inherent  in  it,  and  which  should  re- 
main without  deterioration  through  various  processes  incident 
to  the  manufacture  from  it  of  finished  products  of  other  forms. 

Cables  in  service  are  subject  to  the  destroying  forces  of  sud- 
den strains,  alternations  of  sudden  and  steady  heavy  strains, 
heavy  steady  strains,  abrasion,  and  corrosion  ;  and  the  danger 
from  each  takes  precedence  in  the  order  given. 

The  relative  importance  of  these  sources  of  danger  indicates 
that  iron  which  is  best  adapted  for  cables  is  that  which  pos- 
sesses great  power  to  resist  both  sudden  and  steady  strains,  and 
that  neither  of  these  qualities  in  excess  will  compensate  for  a 
deficiency  in  the  other. 

The  strength  of  the  cable  is  but  that  of  the  weakest  link,  and 
the  strength  of  this  link  but  that  of  the  weakest  part :  therefore, 
in  order  that  a  cable  shall  be  strong  and  reliable,  the  weakest 
part  of  the  weakest  link  must  be  made  as  strong  as  possible. 

The  weakest  part  of  nearly  every  link  is  the  weld.  With 
certain  types  of  iron  the  weld  is  much  weaker  than  with  others : 
hence  we  consider  that  the  prime  elements  of  value  in  a  cable- 
iron  are  power  to  resist  sudden  strains,  and  to  be  welded  thor- 
oughly without  loss  of  strength.  By  the  former  we  insure 
against  the  greatest  danger,  and  by  the  latter  against  the 
frequently  repeated  ordinary  dangers. 

We  were  not  able  to  obtain  any  information  of  value  as  to 
the  qualities  of  various  American  irons  in  these  two  respects ; 
and  we  therefore  resolved  upon  making  a  series  of  experimental 
investigations,  by  the  results  of  which  we  hoped  to  be  able  to 
form  a  correct  judgment. 


4  WROUGHT-IBON  AND   CHAIN-CABLES. 

THE  BAR.  — PART  I. 

-#~ 

Our  plan  of  investigation  was  to  first  ascertain,  by  means  of 
tension  tests  made  upon  bars  of  such  irons  as  we  could  procure, 
the  amount  of  strength,  elasticity,  &c.,  which  would  be  found 
to  exist  in  ordinary  American  bar  iron ;  next,  by  tests  by  im- 
pact upon  the  same  irons,  to  ascertain  their  relative  powers  to 
resist  sudden  strains;  and  finally,  having  ascertained  these 
essential  points  in  the  material,  to  make  from  each  iron  a  num- 
ber of  cable-links,  and  by  tension  to  find  their  strength  and 
uniformity,  and  the  degree  of  dependence  to  be  placed  upon 
the  welds. 

To  carry  out  these  investigations,  we  procured  bars  of  round 
iron  of  sizes  such  as  are  usually  used  in  the  manufacture  of 
cables ;  viz.,  from  two-inch  diameter  to  one  inch,  from  the  fol- 
lowing rolling-mills  and  dealers  in  iron,  viz.,  Burden  &  Sons  of 
New  York,  Bentoni  of  Pennsylvania,  Burgess  of  Ohio,  Cata- 
sauqua  of  Pennsylvania,  New-Jersey  Iron  and  Steel  Company 
of  New  Jersey,  Niles  Iron  Company  of  Ohio,  Phoenix  of 
Pennsylvania,  Pembroke  of  Massachusetts,  Pencoyd  of  Penn- 
sylvania, Tredegar  of  Virginia,  Trego  and  Thompson  of  Mary- 
land, Sligo  of  Pennsylvania,  Tamaqua  of  Pennsylvania,  Wyeth 
Brothers  of  Maryland,  and  many  other  bars  of  unknown 
origin. 

The  experiments,  upon  the  results  of  which  our  report  is 
based,  comprise  the  details  of  all  physical  phenomena  observed 
by  us  while  testing  to  destruction  nearly  two  thousand  bar  test- 
pieces  by  the  strain  of  tension,  over  fifteen  hundred  by  the 
strain  of  percussion,  and  nearly  five  hundred  cable-links,  made 
in  all  respects  as  for  service. 

The  tension-tests  upon  bars  were  made  both  upon  bars  in 
their  normal  condition,  and  upon  others  from  which  a  portion 
of  the  surface  had  been  turned  away.  Those  by  impact  were 
made  upon  portions  of  the  same  bars  which  had  been  tested 
by  tension,  and  those  upon  chain-links  from  other  portions  of 
the  same  bars.  The  Navy  Department  placed  at  our  service 


THE   BAR.  5 

the  facilities  of  the  Washington  Navy  Yard,  which  included 
the  use  of  forges  and  of  two  testing-machines  for  making 
tension-tests ;  also  of  such  records  as  we  desired,  and  of  a  large 
quantity  of  contract  chain-iron,  which  it  was  deemed  advisable 
to  examine. 

A  brief  description  of  our  testing-machines,  and  of  our 
methods  of  testing,  with  a  few  physical  phenomena  we  have 
observed,  will  enable  the  terms  used  in  the  report  to  be  under- 
stood. 

TESTING-MACHINES,  AND  METHODS  OF  TESTING. 

In  order  that  we  might  obtain  the  tensile  strength,  elastic 
limit,  ductility,  &c.,  of  round  bars,  our  first  test  was  by  tension 
upon  full-sized  bars,  from  which  the  outer  portion  had  not  been 
removed.  These  tests  were  made  by  means  of  the  "chain- 
proving  machine,"  at  the  Washington  Navy  Yard,  which  in  this 
report  is  called  "testing-machine  A."  This  machine  consists 
of  a  long  trough,  in  which  a  fifteen-fathom  section  of  cable  can 
be  stretched  by  means  of  a  hydraulic  pump,  to  which  it  is  con- 
nected at  one  end,  while  the  other  end  is  made  fast  to  a  holder, 
which  in  turn  connects  with  a  system  of  levers,  by  which  the 
stress  is  weighed  by  means  of  weights  placed  upon  a  platform 
at  the  extremity  of  the  long  lever. 

The  capacity  of  the  machine  is  three  hundred  thousand 
pounds,  and  the  levers  are  so  adjusted  that  a  weight  of  one 
pound  upon  the  platform  balances  two  hundred  pounds  of 
stress. 

The  pieces  to  be  tested  were  sections  of  the  bar  at  least  eight 
times  the  diameter  in  length,  and  originally  fitted  with  loops  of 
larger-sized  iron,  welded  to  the  ends. 

Additional  tests  by  tension  were  made  upon  many  of  the 
irons  by  means  of  cylindrical  test-pieces  turned  from  the  bars, 
and  ruptured  by  the  "  Rodman  Dynamometer,"  called  in  this 
report  "  testing-machine  B." 

The  results  obtained  by  this  machine  agree  very  closely,  in 
some  cases,  with  those  obtained  by  testing-machine  A,  and  in 


6  WROUGHT-IKON  AND   CHAIN-CABLES. 

others  differ  widely.  A  portion  of  these  differences  is  probably 
due  to  differences  in  the  -accuracy  of  the  two  machines  and 
methods,  and  others  to  a  natural  difference  in  the  character 
of  the  metal  as  developed  by  the  entire  bar,  and  by  a  portion 
of  the  core  and  adjacent  iron. 

This  machine  holds  the  specimen  to  be  tested  by  means  of 
clamps. 

The  capacity  of  the  machine  is  one  hundred  thousand  pounds, 
and  it  will  weigh  a  stress  of  ten  pounds  with  accuracy. 

NOTES  UPON  THE  "  RECOKDS  OF  BAKS  TESTED  BY  TENSION." 

Column  headed  "  Diameter"  —  The  strength  per  square  inch 
of  a  bar,  as  deduced  from  the  stress  at  which  the  entire  bar  has 
been  torn  asunder,  cannot  be  correctly  ascertained,  except  the 
diameter  of  the  bar  be  carefully  calipered:  the  nominal  size 
and  the  exact  size  seldom  coincide ;  and  at  times  we  have  found 
variations  of  four-hundredths  of  an  inch,  which  variation  is 
sufficient  to  produce  important  errors. 

Areas.  —  The  "  original  area "  is  that  which  corresponds  to 
the  diameter  of  the  piece  before  test;  the  "reduced  area"  cor- 
responds with  the  least  diameter  after  rupture ;  the  "  tensile 
limit  area  "  corresponds  with  the  least  diameter  at  the  highest 
stress  the  piece  sustains. 

Length.  —  The  length  of  the  clear  cylindrical  portion  be- 
tween punch-marks  is  measured  before  the  stress  is  applied, 
and  after  fracture.  In  testing  with  the  machine  B  it  is  also 
measured  at  the  "  tensile  limit." 

Percentage  of  Elongation.  —  This  element,  as  given  in  many 
tables,  is  of  little  value,  the  percentage  being  greatly  dependent 
upon  the  original  length  of  the  specimen.  When  this  is  not 
given,  the  percentage  is  of  no  value. 

The  following  experiment  will  make  this  clear :  From  a  bar 
of  If"  iron,  of  very  uniform  character,  three  test-pieces  were 
prepared,  which  were  in  all  respects  similar,  except  in  length. 
The  first  was  75,  the  second  20,  and  the  third  10  inches  long. 


THE  BAR.  7 

• 

They  were  pulled  asunder,  and  the  first  was  found  to  have 
elongated  14  inches,  or  18.64  per  cent  of  the  original  length; 
the  second  had  elongated  4.36  inches,  or  21.8  per  cent ;  and  the 
third  2.22  inches,  or  22.2  per  cent.  Our  records  supply  many 
confirmatory  results. 

First  Stretch.  —  The  bar  being  fastened  to  the  holders,  a 
pair  of  large  dividers  was  adjusted  to  punch-marks,  and  the 
stress  slowly  applied ;  at  the  instant  the  elongation  was  suf- 
ficient to  draw  one  punch-mark  clear  of  the  dividers'  point,  the 
stress  was  weighed,  and  recorded  as  first  stretch. 

Ultimate  stress  is  the  stress  which  represents  the  highest 
which  has  been  withstood  by  the  specimen ;  but  it  was  not  the 
amount  which  finally  produced  the  rupture :  this  stress  pro- 
duced a  weakening,  from  which,  had  the  specimen  been  rested, 
it  would  have  recovered ;  by  continuing  it,  the  specimen  finally 
parted  at  much  less. 

Original,  Fractured,  and  Tensile  Limit  Areas.  —  The  measure- 
ments taken  at  the  "tensile  limit"  introduce  a  new  method 
by  which  the  comparative  values  of  different  irons  may  be 
estimated. 

Ordinarily  the  tenacity  of  iron  is  expressed  in  the  strength 
per  square  inch  of  the  sectional  area  of  the  test-piece  before 
its  form  has  been  changed  by  stress. 

Kirkalcly  suggested,  as  a  more  just  method,  that  the  area 
corresponding  to  the  diameter  of  the  fractured  surfaces  should 
be  adopted  as  the  limit  of  measurement. 

Our  experiments  lead  us  to  believe  that  between  these 
extremes  of  original  and  fractured  areas  there  is  an  inter- 
mediate area  which  can  be  used  with  profit,  which  is  that 
which  corresponds  with  the  least  diameter  of  the  test-piece  at  the 
stress  which  marks  the  highest  point  of  resistance  to  continually 
increasing  strains.  This  point  we  have  termed  the  "  tensile 
limit." 

There  are  practical  difficulties  encountered  in  measuring 
accurately  the  diameter  of  the  fractured  surfaces.  After  the 
test-piece  has  been  pulled  asunder,  there  is  a  difficulty  in  joining 


8  WROUGHT-IRON  AND   CHAIN-CABLES. 

perfectly  the  two  fractured  surfaces,  and  frequently  the  line  of 
surface  is  not  at  right  angles  with  the  axis  of  the  cylinder :  this 
necessitates  two  measurements,  —  one  of  the  greatest  and  one 
of  the  least  diameter,  and  an  interpolation,  —  and,  in  making 
these  measurements,  there  are  chances  of  error,  even  if  the  line 
of  fracture  is  at  right  angles,  which  are  increased  when  it  is 
not. 

The  tensile  strength  per  square  inch  of  original  area  is  more 
liable  to  be  free  from  errors  arising  from  inaccuracy  than  is 
that  of  the  fractured  area.  But  neither  of  these  measure- 
ments provides  us  with  a  standard  by  which  we  can  judge 
of  the  relative  amount  of  change  of  form  that  takes  place 
with  different  irons  at  the  moment  when  they  finally  cease 
to  resist  an  increase  of  stress;  this  deficiency  is  supplied 
in  the  area  at  the  tensile  limit,  which  area  corresponds  to 
the  diameter  of  the  test-piece,  at  the  instant  when  affected 
by  the  highest  stress  the  material  is  capable  of  resisting, 
and  not  by  subsequent  stress  applied  to  a  rapidly -yielding 
metal. 

Length  of  Test-Piece.  —  Not  only  the  "  percentage  of  elonga- 
tion "  obtained  by  testing  a  piece  of  iron,  but  the  strength,  de- 
pends upon  the  length  of  the  test-piece.  Our  experiments 
show,  that,  if  an  iron  is  judged  by  a  test-piece  whose  length  is 
less  than  four  diameters,  the  judgment  is  wrong. 

STRENGTH  AND  ELASTIC  LIMIT  OF  ROUND  BAR-IRON. 

In  the  following  table  the  stresses  by  tension  required  to 
rupture  many  of  the  bars  we  have  tested  are  arranged  in  their 
relative  order,  the  greatest  stress  required  being  given  prece- 
dence upon  each  size. 

In  the  columns  in  which  the  stress  is  reduced  to  the  square 
inch,  the  areas  corresponding  to  the  actual  diameters  of  the 
bars  have  been  used.  This  gives  a  more  correct  estimate  of 
the  relative  order  of  tenacity  than  the  diameter  given  in  the 
first  column,  by  using  which  bars  would  frequently  gain  or  lose 


THE  BAB. 


9 


in  precedence  on  account  of  excess  or  lack  of  material,  some 
being  rolled  "full,"  and  others  "scant." 

In  the  column  "  Standard  for  Size,"  the  strength  which 
we  have  found  best  adapted  for  cable-iron  is  placed  for  com- 
parison. 

The  elastic  limit  as  given  is  not  from  perfectly  accurate  data : 
it  is  simply  the  amount  of  stress  which  produced  the  first  per- 
ceptible change  of  form,  divided  by  the  bar's  area. 


Strength  per  Original  Area,  per  Square  Inch,  and  Elastic  Limit  per  Square 
Inch,  of  959  Round  Bars. 


. 

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12,311 

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54,360 

54,687 

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11,388 

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53,050 

53,850 

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10,881 

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53,035 

32,410 

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10,359 

52,275 

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50,300 

50,149 

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5 

49,660 

52,267 

32,019 

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11 

16,977 

55,450 

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F 

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15,928 

52,050 

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K 

2 

72,960 

59,461 

36,501 

65,914 

F 

11 

17,644 

57,660 

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P 

2 

73,200 

56,876 

36,868 

C 

1 

71,040 

57,897 

32,469 

f 

F 

4 

22,746 

51,546 

35,933 

D 

2 

72,300 

57,977 

31,996 

P 

2 

70,704 

55,782 

35,596 

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F 

4 

30,850 

50,630 

33,931 

Px 

2 

70,250 

56,334 

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N 

2 

69,300 

56,478 

33,251 

1 

K 

13 

48,480 

61,727 

.... 

43,665 

Fxl 

5 

68,460 

55,253 

34,784 

D 

1 

48,000 

61,115 

33,486 

D 

1 

68,160 

55,550 

28,166 

0 

1 

46,000 

57,363 

37,415 

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1 

67,200 

53,893 

32,712 

Fxl 

5 

45,040 

55,768 

34,729 

Fx2 

3 

66,600 

55,132 

38,603 

P 

2 

44,500 

57,807 

39,230 

Fx3 

2 

66,400 

53,247 

32,520 

A 

3 

44,126 

54,690 

34,881 

A 

3 

66,112 

53,897 

27,643 

Fx2 

3 

44,450 

56,790 

36,885 

M 

20 

65,960 

53,752 

.... 

Fx3 

2 

42,350 

53,915 

36,336 

M 

20 

65,850 

54,090 

.... 

F 

2 

41,600 

51,921 

31,300 

F 

2 

64,990 

52,970 

32,075 

D 

8 

41,547 

52,900 

F 

2 

64,700 

52,729 

39,608 

F 

5 

40,660 

52,819 

32J267 

M 

20 

64,285 

53,022 

.... 

F 

4 

40,309 

51,400 

34,600 

F 

5 

62,520 

52,620 

33,220 

0 

1 

61,400 

50,040    30,730 

K 

3 

60,096 

60,458 

37,344 

54,261 

1 

D 

1 

58,700 

59,582 

33,597 

Te 

P 

94 

74,427 

54,518 

35,898 

72,133 

C 

2 

57,125 

57,470 

31,900 

Fxl 

5 

57,620 

56,434 

34,682 

!•§• 

M 

48 

86,862 

58,926 

37,548 

78,607 

P 

2 

56,500 

57,498 

41,311 

M 

35 

87,496 

57,649 

38,578 

10 


WEOUGHT-IRON  AND  CHAIN-CABLES. 


c 

1 

Strength. 

o 

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1 

Strength. 

• 

^ 

2 

"o 

A 

£5 

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2 

0 

fl 

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02 

5 

ll 

£ 

0* 

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«OQ 

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02 

02 

00 

in. 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

in. 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

If 

D 

1 

86,800 

58,021 

32,152 

If 

Px 

2 

115,500 

54,689 

33,427 

K 

2 

82,248 

55,790 

31,034 

o 

A 

2 

111,984 

54,334 

32,163 

C 

1 

81,600 

54,949 

31,030 

D 

1 

111,360 

53,695 

30,087 

M 

28 

80,693 

54,373 

35,820 

Fx3 

2 

111,300 

53,339 

33,540 

N 

2 

81,200 

54,277 

33,622 

Fxl 

5 

110,140 

53,537 

34,335 

Fxl 

5 

80,360 

52,968 

33,275 

D 

1 

110,500 

53,614 

30,664 

Fx3 

2 

80,000 

52,733 

34,606 

J 

1 

109,400 

52,748 

E 

1 

79,296 

52,254 

25,930 

E 

1 

109,245 

52,675 

33,  745 

A 

3 

78,994 

53,557 

33,650 

Fx2 

3 

108,800 

53,438 

35,870 

P 

1 

78,624 

52,556 

30,802 

H 

1 

108,500 

52,314 

29,364 

F 

5 

78,580 

52,537 

34,469 

E 

1 

108,384 

51,946 

27,695 

F 

2 

78,300 

52,339 

39,103 

0 

1 

108,000 

52,401 

34,012 

M 

4 

78,150 

53,016 

35,379 

F 

2 

107,520 

52,163 

33,907 

Fx2 

3 

76,333 

51,487 

35,911 

G 

1 

106,200 

51,205 

33,318 

F 

2 

77,235 

51,296 

31,992 

F 

2 

105,500 

50,529 

35,390 

0 

1 

72,400 

50,594 

34,940 

F 

5 

105,440 

50,970 

33,625 

C 

1 

101,700 

49,030 

31,099 

1  7 

P 

1 

89,300 

53,345 

.... 

85,339 

16 

E 

1 

87,552 

53,944 

32,542 

T6 

K 

1 

130,000 

56,595 

38,310 

114,770 

G 

1 

86,400 

53,238 

32,534 

B- 

1 

121,150 

54,181 

.... 

B 

4 

84,862    52,287 

32,411 

J 

1 

121,000 

54,114 

.... 

C 

1 

84,000  !  51,756 

32,655 

B 

3 

118,273 

52,895 

33,145 

J 

1 

81,800 

50,400 

.... 

E 

1 

116,544 

52.120 

35,549 

G 

1 

115,800 

57,789 

34,160 

1^ 

M 

12 

102,125 

57,052 

38,417 

92,322 

C 

1 

111,400 

49,821 

83,184 

K 

2 

101,280 

57,317 

33,412 

D 

1 

101,200 

56,505 

32,496 

jA 

K 

1 

139,200 

57,874 

.... 

122,745 

M 

25 

99,064  1  55,466 

34,780 

Px 

2 

131,900 

54,212 

33,908 

M 

26 

98,730  !  55,131 

33,771 

C 

5 

130,836 

54,410 

31,354 

P 

2 

98,300  |  54.159 

33,140 

P 

2 

130,050 

52,844 

33,842 

M 

17 

98,047 

54,540 

Fxl 

5 

129,500 

53,846 

36,573 

C 

4 

97,921 

55,404 

sV,770 

H 

1 

129,400 

53,800 

27,856 

E 

1 

97,920 

55,415 

32,869 

N 

2 

129,350 

55,018 

34,283 

M 

20 

97,665 

54,816 

34,716 

D 

1 

128,600 

53,472 

31,892 

Px 

2 

97,350 

54,354 

34,617 

J 

1 

128,100 

53,264 

M 

27 

97,095 

54,095 

35,544 

D 

1 

126,720 

52,699 

27*,817 

E 

1 

96,384 

54,544 

33,027 

Fx3 

2 

126,100 

53,154 

35,323 

P 

1 

95,904 

52,868 

29,636 

E 

1     124,128 

51,606 

26,541 

M 

20 

95,810 

53,512 

A 

2  I  123,340 

51,509 

29.404 

M 

23 

94,809 

52,941 

F 

1 

121,920 

50,690 

32,229 

Fx3 

2 

94,600 

52,819 

34,840 

G 

1 

121,200 

50,395 

36,254 

Fxl 

5 

94,520 

53,491 

34,307 

C 

1 

121,000 

50,312 

30,852 

M 

4 

93,500 

52,736 

34,901 

F 

2 

120,200 

50,547 

35,954 

N 

2 

93,400 

53,555 

34,690 

Fx2 

3 

120,1  f  7 

52,314 

35,320 

C 

1 

93,100 

52,700 

35,880 

E 

1 

119,808 

49,816 

31,214 

H 

1 

92,700 

52,462 

29,992 

F 

5 

117,740 

49,738 

28,907 

D 

1 

92,160 

52,155 

27,708 

O 

1 

116,500 

50,129 

32,271 

A 

2 

91,680 

51,884 

28,794 

F 

2 

91,875 

51,994 

32,054 

^  i  H 

K 

1 

148,800 

56,577 

.... 

130,965 

0 

1 

91,400 

50,919 

32,312 

B 

4 

138,507 

53,655 

.... 

F 

5 

90,925 

51,456 

34,591 

C 

1 

131,500 

50,969 

30,814 

Fx2 

3 

90,967 

51,481 

34,917 

129,850 

50,310 

33,565 

J 

1 

90,200 

51,047 

E 

129,792 

50,307 

29,767 

M 

1 

87,100 

49,292 

32',597 

J 

126,300 

48,953 



If 

N 

2 

119,000 

56,344 

35,889 

107,040 

11 

K 

154,080 

55,803 

31,031 

139,430 

K 

4 

118,463 

57,132    35,026 

C 

150,336 

54,447 

32,334 

M 

10 

119,800 

57,402  '  35,701 

D 

149,000 

53,100 

32,074- 

P 

2 

117,500 

55,634 

33,522 

N 

148,350 

54,004 

33,610 

C 

4 

116,892 

56,227 

33,207 

Fxl 

146,780 

52,875 

35,641 

THE  BAB. 


11 


g 

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!a 

i 

Strength. 

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2 

H 

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f&s. 

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Ibs. 

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11 

Fx3 

2 

146,500 

53,361 

35,032 

2 

F 

5 

149,960 

47,569 

28,792 

0 

P 

2 

145,200 

52,505 

32,312 

O 

2 

151,640 

48,249 

31,413 

E 

2 

142,900 

50,880 

27,100 

D 

1 

149,800 

49,146 

33,068 

D 

1 

142,080 

51,459 

27,816 

D 

1 

142,100 

46,151 

36,050 

Px 

2 

142,000 

51,762 

32,261 

M 

2 

141,300 

50,363 

IB 

M 

1 

178,600 

51,559 

.... 

A 

2 

141,120 

50,584 

2*8,713 

M 

1 

171,200 

49,422 

F 

2 

140,925 

51,039 

33,067 

Fx2 

3 

139,000 

51,159 

33,970 

8 

Jtt 

1 

184,600 

50,481 

.... 

F 

2 

136,600 

49,744 

35,615 

M 

1 

186,000 

51,225 

.... 

F 

3 

134,500 

49,355 

32,855 

A 

1 

170,784 

48,382 

30,459 

F 

2 

132,250 

48,670 

23,250 

O 

1 

129,000 

47,478 

30,842 

2T6 

M 

2 

200,000 

51,666 

.... 

115 

M 

1 

156,000 

51,707 

148,137 

21 

M 

1 

210,400 

51,530 

.... 

M 

2 

155,300 

51,474 

.... 

- 

M 

1 

205,800 

515296 

.... 

M 

1 

154,000 

51,242 

.... 

F 

3 

195,977 

49,290 

32,163 

F 

2 

195,476 

49,164 

31,966 

2 

K 

1 

194,880 

60,213 

31,441 

157,080 

F 

1 

192,700  |  48,898 

K 

1 

188,160 

57,567 

30,839 

F 

1 

189,600 

48,812 

.... 

Px 

2 

167,900 

52,914 

31,198 

P 

2 

184,700 

46,866 

28,241 

M 

1 

167,600 

52,820 

.... 

M 

1 

156,000 

49,164 

.... 

2i 

F 

2 

237,930 

48,475 

28,932 

E 

1 

167,712 

51,818 

27,318 

F 

3 

232,776 

47,428 

29,941 

P 

2 

165,600 

51,684 

33,104 

F 

2 

232,400 

47,344 

29,758 

P 

2 

161,300 

50,834 

31,878 

N 

165,400 

52,127 

32,461 

2| 

F 

3 

275,889 

46,446 

26,333 

N 

163,000 

51,370 

32,460 

Fxl 

163,420 

52,011 

34,702 

3 

F 

3 

337,603 

47,761 

26,400 

C* 

160,704 

51,153 

29,335 

D* 

160,700 

51,146 

28,567 

3^ 

F 

2 

390,019 

47,014 

24,591 

P 

159,840 

49,872 

29,953 

Fx2 

2 

155,500 

50,000 

36,184 

34 

F 

o 

452,191 

47,000 

24,961 

Fx3 

2 

159,500 

50,763 

33,172 

A 

9 

157,588 

50,171 

28,983 

3f 

F 

2 

515,423 

46,667 

23,636 

F 

2 

152,260 

48,596 

27,634 

F 

2 

151,900 

47,812 

35,864 

4 

F 

2  !  582,100 

46,322 

23,430 

THE  BAR.— PART  II. 

INVESTIGATION  OF  THE  EFFECT  OF  DIFFERENCES   IN   THE 
AMOUNT  OF  REDUCTION  BY  THE  ROLLS. 

In  procuring  material  upon  which  to  make  tests  by  tension 
both  in  the  bar  and  link  form,  our  custom  was  to  purchase  from 
manufacturers  at  least  one  bar  of  each  size  ordinarily  used  in 
chain-cables.  Testing  these  bars  in  their  normal  condition  by 


12  WROUGHT-IEON  AND  CHAIX-CABLES. 

tension,  it  became  evident  that  the  strength  of  the  different 
sizes  was  not  in  proportion  to  their  areas ;  but  that,  on  the  con- 
trary, there  existed  a  variation  in  proportional  strength  which 
was  in  accord  with  variations  in  the  diameter  of  the  bars.  In 
general  terms  it  was  found,  that,  as  the  diameter  of  the  bar 
became  less,  the  strength  per  square  inch  increased;  but,  in 
comparing  the  results  obtained  from  a  number  of  such  sets  of 
bars,  it  became  evident  that  the  increase  of  strength  from  be- 
tween the  two  extremes  of,  say,  2"  and  V  was  not  created  by 
a  series  of  uniform  steps  upon  each  successive  reduction,  but 
that  there  was  one  point  in  the  reduction  where  a  decrease  took 
the  place  of  the  usual  increase,  and  that  from  this  point  the 
increase  again  began,  and  generally  by  more  rapid  steps. 

Thus  the  2"  bar  was  of  less  strength  than  the  1|";  the  latter 
was  of  less  than  the  If",  which  was,  in  turn,  less  than  the  1|", 
but  the  strength  of  the  If"  was  greater  than  that  of  the  1J"; 
the  If",  1|",  1 J",  and  sometimes  the  1",  being  each  of  increased 
strength  in  the  order  given. 

We  found,  that,  with  a  set  of  bars  of  the  above  sizes,  the  dif- 
ference in  proportional  strength  between  the  extremes  was  from 
four  to  six  thousand  pounds;  that  the  tenacity  of  the  If"  ex- 
ceeded that  of  the  2"  from  two  to  three  thousand  pounds,  and 
that  of  the  1J"  from  one  to  three  thousand  pounds. 

As  we  became  fully  satisfied  that  these  variations  did  exist  in 
all  uniform  irons  which  we  examined,  we  considered  ourselves 
justified  in  assuming  that  they  would  probably  occur  generally 
with  other  irons,  and  that,  so  occurring,  their  existence  should 
be  taken  into  consideration  in  any  attempt  to  calculate  the 
strength  of  links  or  other  articles  made  from  bar-iron  of  various 
sizes. 

Experiments  at  the  testing-machine  afforded  no  indications 
by  which  we  could  determine  any  thing  in  regard  to  the  causes 
of  these  variations.  We  therefore  undertook  to  watch  all  the 
processes  connected  with  the  manufacture  of  a  "  set  of  bars," 
in  hopes  that  while  so  doing  we  should  be  able  to  detect  the 
hidden  reason. 


THE  BAR. 


13 


At  our  first  visit  to  a  rolling-mill,  a  set  of  bars  were  prepared 
of  carefully  selected  material,  and  careful  notes  were  taken  dur- 
ing the  process  of  manufacture,  which  are  herewith  reproduced. 

There  were  two  bars  of  each  size  rolled. 

Notes  in  Regard  to  Manufacture  of  Iron  F,  Second  Lot. 


c 

m 

g  > 

NUMBER  OF 

&* 

rt 

1C 
C     • 

NUMBER  OF 

3 

.2  5 

0 

PASSES. 

B 

|j 

r-    O 

PASSES. 

a 

<4~< 

Is 

.5  ££ 

"^    00 

*4H 

£S      J 

o 

.**   • 

c 

8 

02 

g° 

II 

Square 
RolL. 

Round 

Rolls. 

s 

02 

^* 

5° 

u 

Square  Round 
Rolls.    Rolls. 

Ji 

h.ra. 

m. 

h.m. 

m. 

'  2' 

f 

6"  x  10"  x  26" 

2.06 

15 

9 

09 

£ 

6"  x  6"  x  26" 

.32 

13 

8 

05i 

2 

6    x  10    x  26 

2.15 

15 

9 

08 

6    x  6    x  21 

.00 

15 

8 

05 

1 

6    x  10    x  24 

2.02 

15 

9 

07 

3 

6    x  6    x  21 

.04 

15 

8 

04 

I 

6    xlO    x24 

2.23 

15 

8 

07 

£ 

6    x  6    x  14 

.20 

15 

8 

04 

1] 

6    xlO    x21 

1.40 

17 

9 

07 

» 

6    x6    x!4 

.20 

15 

8 

04 

I] 

6    x  10    x  21 

1.49 

17 

9 

06 

1 

6    x6    x!2 

.10 

15 

8 

04 

JH 

6    x  10    x  18 

1.35 

15 

9 

06 

1 

6    x  6    x  12 

1.10 

15 

8 

04 

1 

6    xlO    x!8 

1.40 

15 

9 

06 

6    x4    x!4 

1.10 

15 

8 

04 

4 

6    x    6    x26 

1.26 

13 

10 

05 

1 

6    x4    x!4 

1.10 

15 

8 

04 

A  study  of  these  notes  indicated  that  if  there  proved  to  ex- 
ist any  marked  difference  in  the  characteristics  of  the  different 
bars,  it  could  not  be  considered  as  owing  to  want  of  care  in 
their  preparation.  No  accident  caused  delays  while  passing 
through  the  rolls,  and  the  number  of  passes  was  quite  uniform. 

By  contrasting  the  areas  of  these  piles  with  those  of  the 
resulting  bars,  it  will  be  seen  that  there  was  a  very  different 
amount  of  reduction  produced  by  the  rolls,  varying  from  5.23 
to  2.76  per  cent.  The  tenacity  of  these  bars  agreed  to  some 
extent  with  the  amount  of  reduction,  but  not  so  closely  as  had 
been  expected. 

The  experiment  was  repeated  by  watching  another  set  of 
bars  rolled  by  the  same  mill,  of  the  same  material,  the  set  com- 
prising bars  of  all  sizes,  ranging  by  j"  from  4"  diameter  to  |" 
diameter.  The  iron  was  very  carefully  heated,  and  received 
a  nearly  uniform  number  of  passes  through  the  rolls. 

The  dimensions  of  the  piles,  the  proportion  borne  by  the 
areas  of  the  resultant  bars,  and  the  tensile  strength  and  elastic 


14 


WROUGHT-IEOX  AXD   CHAIN-CABLES. 


limit  per  square  inch  of  the  bars,  as  found  by  tests  made  upon 
them  entire  and  upon  cylinders  turned  from  the  cores,  are  given 
in  the  following  table. 

IROX  F,  THIRD  LOT. 

Comparisons  of  the  Reductions  by  the  Rolls,  with  the  Effects  upon  Tenacity  and 
Elastic  Limit,  of  Iron  F,  Third  Lot. 


Size  of  Bar. 

Area  of  Pile. 

Areaof  Bar 
in  percent 
of  area  of 
rile. 

TENSILE  STRENGTH. 

ELASTIC  LIMIT. 

Entire  Bar. 

Core. 

Entire  Bar. 

Core. 

Sq.  in. 

rer  cent. 

Pounds. 

Pounds. 

Pounds. 

Pounds. 

4 

80 

15.70 

46,322 

. 

23,430 

3| 

80 

13.80 

. 

46,6d7 

.     . 

23,636 

85 

80 

12.03 

47,000 

. 

24,961 

3» 

80 

10.37  ' 

. 

47,014 

.     . 

24,591 

3 

80 

8.83 

, 

47,761 

. 

26,400 

23 

80 

7.42 

, 

46,466 

. 

26,333 

2i 

80 

6.13 

47,344 

47,428 

29,  58 

29,941 

2J 

72 

5.52 

48,505 

49,290 

31,267 

32.163 

2 

72 

4.36 

47,872 

48,280 

35,864 

31,892 

36 

7.67 

49,744 

49,370 

35,615 

37,042 

36 

6.68 

50,547 

48,792 

35,954 

38,992 

36 

5.76 

50,529 

49,144 

35,394 

34,208 

36 

4.90 

50,820 

61,838 

35,087 

36,467 

36 

4.12 

52,339 

48,819 

39,103 



1 

36 

3.41 

52,729 

49,801 

39,608 

40,534 

1 

25 

3.96 

50,149 

50,530 

35,493 

37,771 

1 

25 

3.14 

51,921 

51,128 

39,066 

38,596 

331 

4.91 

50,716 

50,374 

33,931 

33,931 

12! 

3.60 

50,673 

50,276 

33,933 

35,933 

12| 

2.50 

52,297 

51,431 

34,450 

34,545 

9 

2.17 

52,275 

52,775 

38,445 

39,126 

9 

3.68 

54,098 

54,108 

38,475 

40,098 

3 

1.60 

57,000 

59,585 

Lost 

Lost 

A  study  of  the  table  shows  first  that  upon  the  nine  succes- 
sively decreasing  sizes,  viz.,  from  4"  to  2",  there  was  but  one  ex- 
ception to  a  constant  rise  in  tenacity  accompanying  the  increase 
of  reduction  by  the  rolls,  and  that  the  elastic  limit  rose  upon 
each  successive  step  with  two  exceptions,  which  are  very  slight, 
it  falling  off  350  pounds  in  one  and  67  pounds  in  another  in- 
stance ;  the  tenacity  of  the  2"  (4.36  per  cent  of  pile)  being  over 
that  of  the  4"  (15.70  per  cent  of  pile)  1,106  pounds,  and  the 
elastic  limit  8,462  pounds. 

From  the  If  (7.67  per  cent  of  pile)  to  the  1 J"  (3.41  per  cent 
of  pile),  the  iron  was  somewhat  irregular,  and  there  was  but  a 


THE  BAR.  15 

slight  rise  in  tenacity,  viz.,  431  pounds,  but  in  the  elastic  limit 
the  rise  was  4,993  pounds. 

The  tenacity  of  the  |"  (4.91  per  cent  of  pile)  was  but  104 
pounds  greater  than  that  of  the  1£"  (4.90  per  cent  of  pile),  that 
of  the  |"  (2.50  per  cent  of  pile)  nearly  corresponding  with  that 
of  the  If"  (4.12  per  cent  t>f  pile). 

The  effect  of  reduction  was  most  marked  on  the  smaller  sizes, 
the  -|"  (2.17  per  cent  of  pile)  having  nearly  5,000  pounds  less 
tenacity  than  the  -J"  (1.60  per  cent  of  pile). 

The  notes  taken  at  the  mill  do  not  indicate  that  either  bar 
was  under  or  over  heated ;  but  there  are  indications  that  the 
1J"  bar  was  overheated,  inasmuch  as  the  strength  of  the  core 
exceeded  that  of  the  entire  bar. 

So  far  as  this  experiment  was  expected  to  account  for  the 
usually  found  greater  strength  of  the  If"  bar,  it  proved  a  fail- 
ure, for  it  was  weaker  than  the  bars  immediately  succeeding  or 
preceding;  but  we  considered  that  the  information  gained  as 
to  the  probable  effect  of  under  and  over  heating  was  of  value. 
The  indications  are  that  if  a  bar  is  underheated  it  will  have  an 
unduly  high  tenacity  and  elastic  limit,  and  that  if  overheated 
the  reverse  will  be  the  case ;  further,  if  underheated  the  strength 
obtained  by  a  cylinder  turned  from  the  core  will  be  less  than 
that  which  would  be  obtained  by  testing  the  entire  bar,  if  the 
diameter  be  small,  and  greater  if  the  cylinder  is  turned  from  a 
large  bar. 

It  is  possible  that  the  above  two  points  are  interdependent, 
as  the  large  bars  are  more  apt  to  be  irregularly  heated  than  the 
small  ones,  and  some  portions  of  the  pile  must  be  in  a  state  fit 
to  roll  before  other  portions  are  sufficiently  heated ;  these  over- 
heated portions  we  turn  off  from  the  bar  to  produce  the  cylin- 
drical test-piece. 

As  in  the  previous  experiment,  we  believed  that  the  thorough 
work  received  by  all  sizes  put  them  in  condition  which  prevent- 
ed the  effect  due  to  a  slight  difference  in  the  reduction  being 
plainly  manifest.  We  therefore  selected  for  another  experiment 
the  bars  of  a  very  slightly  worked  iron ;  viz.,  iron  N. 


UNIVERSITY 


16 


WROUGHT-IRON  AND   CHAIN-CABLES. 


IRON  N. 

Dimensions  of  Piles,  Areas  of  Piles,  of  Bars  in  percentage  of  Areas  of  Piles, 
Tenacity,  Elastic  Limit,  fyc.,  of  Iron  N. 


Area  of  Bars 

Size  of 
Bars. 

Dimensions  of  Piles. 

Area  of 
Piles. 

in 
per  cent  of 

Tensile 
Strength. 

Elastic 
Limit. 

Area  of  Piles. 

Sq.  In. 

Per  cent. 

Pounds. 

Pounds. 

2   " 

6"x4f"x26  " 

27 

11.63 

51,848 

32,461 

_ 

.  6  x4^ 

x21 

27 

10.22 

54,034 

33,610 

1 

6  x4^ 

x21 

27 

8.90 

55,018 

34,283 

1 

6  x4j 

x!64 

27 

7.68 

56,344 

35,889 

1 

4   x3; 

x25 

15 

11.78 

53,550 

34,690 

1 

4  x3^ 

x23 

15 

9.90 

54,277 

33,622 

1 

4  x3' 

-  x!7 

15 

8.18 

56,478 

33.251 

1 

4  x3i 

x!6 

15 

6.62 

56,143 

32,267 

The  above  results  supplied  the  missing  evidence.  With  one 
exception,  the  tenacity  and  elastic  limit  increased  upon  each 
successive  increase  in  the  amount  of  reduction  by  the  rolls,  as 
shown  more  plainly  thus,  where  they  are  arranged  in  the  order 
of  their  reduction:  U"  (6.62  per  cent  of  pile),  56,543;  1|" 
(T.68  per  cent  of  pile),  56,344 ;  U"  (8.18  per  cent  of  pile), 
56,478 ;  U"  (8.90  per  cent  of  pile),  55,018 ;  1|"  (9.90  per  cent 
of  pile),  54,277;  1J"  (10'.22  per  cent  of  pile),  54,034;  2" 
(11.63  per  cent  of  pile),  51,848;  W  (11.78  per  cent  of  pile), 
53,550. 

The  tensile  strength  of  the  2"  bar  was  probably  greater  than 
recorded,  the  iron  being  so  brittle  that  the  head  of  the  test- 
piece  pulled  off,  and  the  bar  could  be  broken  by  sledge-blows, 
without  previous  nicking.  This  iron,  under  every  form  of 
test,  showed,  by  its  marked  contrast  with  iron  F,  the  dis- 
advantages which  follow  too  little  work. 

The  evidence  submitted  is  of  sufficient  value  to  justify  us 
in  asserting  that  variations  in  the  amount  of  reduction  by  the 
rolls  of  different  bars  from  the  same  material  produce  fully  as 
much  difference  in  their  physical  characteristics  as  is  produced 
by  differences  in  their  chemical  constitution. 


THE  BAK. 


17 


In  order  to  ascertain  beyond  question  if  the  rule  would  work 
in  both  directions,  and  if,  by  giving  to  a  series  of  bars  a  uniform 
reduction,  their  tenacity,  &c.,  would  prove  uniform,  the  follow- 
ing experiment  was  made :  — 

One  of  the  leading  manufacturers  of  the  country,  having 
placed  both  the  facilities  of  his  mill  and  as  much  material  as 
we  wished  at  our  service,  three  sets  of  bars  were  rolled,  which 
are  termed  Fx  Nos.  1,  2,  and  3,  all  of  which  were  of  the  same 
material  as  iron  F. 

In  preparing  the  piles  for  the  first  set,  they  were  so  graduated 
that  the  percentage  of  the  pile's  area  borne  by  the  bar  should 
increase  slightly  upon  each  reduction  in  diameter  of  the  bar ;  it 
being  believed  that  the  additional  work  thus  given  to  the 
smaller  sizes  would,  in  a  measure,  counteract  the  possible 
differences  which  might  be  due  to  overheating  of  the  large  and 
underheating  of  the  small  bars. 

The  dimensions  of  piles,  &c.,  are  given  in  the  following 
table,  together  with  the  tensile  strength,  elastic  limit,  &c.,  of 
the  resultant  bars. 

Fx  No.  1. 

Dimensions  of  Piles,  of  Bars  in  per  cent  of  Piles,  Tenacity  and  Elastic  Limit 
of  Series  of  Bars,  of  Fx  No.  1. 


Area  of  Bars 

Size 
of 
Bars. 

Dimen- 
sions of 
Piles. 

Area 
of 
Piles. 

in 
per  cent 
of 

Tensile 
Strength. 

Elastic 
Limit. 

Area  of  Piles. 

In. 

Inches. 

Sq.In. 

Per  cent. 

Pounds. 

Pounds. 

2 

8x10 

80 

3.93 

52,011 

34,702 

11 

8x   9 

72 

3.83 

52,874 

35,641 

If 

8x    8 

64 

3.75 

53,846 

36,573 

if 

6x10 

60 

3.45 

53,537 

34,235 

l{ 

6x   9 

54 

3.27 

53,491 

34,307 

If 

6x   8 

48 

3.09 

52,968 

33,275 

Average  53,121  T.  S.  and 

34,700  E.  L. 

H 

6x   8 

48 

2.55 

55,307 

34,784 

if 

6x   6 

36 

2.76 

56,434 

34,682 

i 

6x    5 

30 

2.62 

55,770 

34,279 

Average  55,837  T.  S.  and 

34,582  E.  L. 

18 


WE  OUGHT-IKON  AND  CHAIN-CABLES. 


The  results  show  a  nearly  uniform  tenacity  for  the  first  six 
sizes,  then  an  increase,  which  remains  quite  uniform  fo*  the 
other  three,  the  elastic  limit  remaining  very  uniform  through- 
out. 

The  tenacity  of  the  2"  bar,  rolled  by  the  usual  process  (iron 
F,  2"),  its  area  being  5.23  per  cent  of  pile,  was  47,569  pounds, 
showing  an  increase  upon  this  size,  by  the  experimental  pro- 
cess, of  4,442  pounds;  and  the  increase  of  the  elastic  limit, 
5,910  pounds,  was  still  more  marked. 

No  explanation,  except  that  they  were  possibly  not  enough 
heated,  accounts  for  the  increased  tenacity  of  the  1J"  and  the 
1"  bars ;  and  the  li"  was,  by  mistake,  rolled  from  too  large  a 
pile. 

A  second  attempt  to  produce  a  set  of  bars  of  uniform 
tenacity  resulted  in  a  complete  failure,  due,  we  were  assured, 
to  a  misunderstanding  in  regard  to  heating  the  piles ;  but  on  a 
third  attempt  we  were  successful,  as  shown  by  the  following 
table,  in  which  the  usual  data  are  given :  • — 

Dimensions  and  Areas  of  Piles,  Areas  of  Bars  in  percentages  of  Piles,  Tensile 
Strength,  Elastic  Limit,  8fc.,  of  Nine  Bars  of  Iron  Fx  No.  3. 


Area  of  Bars 

Bize  of 

Dimensions 

Area  of 

in 

Tensile 

Elastic 

Bars. 

of  Piles. 

Piles. 

per  cent  of 

Strength. 

Limit. 

Area  of  Piles. 

Inches. 

Inches. 

Sq.  In. 

Per  cent. 

Pounds. 

Pounds. 

2 

8x10 

80 

3.92 

50,763 

33,258 

11 

8x10 

80 

3.45 

53,361 

35,032 

1 

8x   9 

72 

3.34 

53,154 

35,323 

li 

8x   8 

64 

3.24 

53,329 

33,520 

1- 

6x   9 

54 

3.27 

52,819 

34,840 

l\ 

6x   7 

42 

3.53 

52,733 

34,606 

1 

6x   6 

36 

3.41 

53,248 

33,520 

1 

6x   5 

30 

3.31 

54,648 

34,695 

1 

5x   5 

25 

3.14 

53,915 

36,287 

The  pile  for  the  2"  was  necessarily  two  small,  as  there  were 
no  rolls  in  the  mills  which  would  take  a  larger  pile.  The 
record  is,  however,  of  value  as  a  contrast  to  that  of  the  other 


THE  BAE.  19 

eight  bars,  the  average  of  whose  tensile  strength,  53,401  pounds, 
and  of  the  elastic  limit,  34,365  pounds,  is  but  slightly  varied 
from  by  any  of  the  bars. 

Two  practical  results  of  value  may  be  deduced  from  this 
investigation  of  the  action  of  the  rolls. 

The  first  is,  that,  as  important  differences  exist  in  the  pro- 
portionate strength  of  different-sized  bars  made  of  the  same 
material,  which  are  due  entirely  to  differences  in  the  processes 
by  which  they  are  manufactured,  and  as  the  elimination  or 
reduction  of  such  differences  would  necessitate  such  a  great 
and  expensive  change  in  the  system  by  which  the  bars  are  pro- 
duced that  it  is  not  probable  that  it  will  be  often  attempted, 
it  is  necessary  that  these  differences  should  be  taken  into 
consideration  when  estimates  of  the  strength  of  any  structure 
in  which  rolled  wrought-iron,  of  different  sizes,  is  introduced, 
are  made,  and  in  all  tables  of  strength  based  upon  the  strength 
of  such  bars. 

Second,  that,  where  the  increased  value  of  the  bars  will 
justify  the  increased  expense  of  their  production,  those  of  2" 
diameter  can  be  increased  in  tensile  strength  over  15,000 
pounds ;  and  it  is  not  improbable  that  bars  of  4"  diameter  can 
have  the  strength  increased  over  60,000  pounds,  with  no  loss 
in  their  power  to  resist  sudden  strains. 


20  WKOUGHT-IRON  AND  CHAIN-CABLES. 


SECTION  IL 

PART  I.  — A  Paper  showing,  by  many  Experiments,  the  Correct  Form  and  Pro- 
portion of  Test-Pieces  to  be  used  in  order  to  procure  correctly  the  Tenacity, 
Elastic  Limit,  8fc.,  of  Various  Metals.  PART  II. — A  Comparison  of  the 
Strength  of  Bars  in  their  Normal  Condition,  with  the  same  after  the  Bars  have 
been  reduced  by  turning  away  the  Surface. 

PART  I.— FORM  AND  PROPORTIONS   OF  TEST-PIECES. 

IN  obtaining  the  results  introduced  in  the  tables  of  records 
of  bars  tested  by  tension,  we  have  used  the  two  testing-ma- 
chines A  and  B. 

By  the  first,  we  have  tested  all  the  bars  of  diameter  greater 
than  one  inch ;  and,  by  the  latter,  bars  in  their  normal  condition 
of  less  than  one  inch  diameter,  and  cylinders  turned  from  the 
larger  bars. 

Our  tests  made  upon  these  cylinders  gave  results  of  tensile 
strength  and  elastic  limit  which  were  so  much  lower  than  the 
manufacturers  of  the  various  irons  considered  their  products 
equal  to,  that  some  dissatisfaction  and  doubt  as  to  their  cor- 
rectness were  expressed. 

Upon  examination,  we  found  that  in  nearly  all  cases  where 
our  results  were  supposed  to  be  erroneous, — on  account  of  a 
lack  of  coincidence  with  results  obtained  in  some  cases  by  the 
experiments  of  private  testers  of  iron,  and  in  others  by  tests 
made  in  government  navy-yards,  by  persons  presumed  to  be 
competent,  —  the  tests  whose  results  cast  doubt  upon  ours  had 
been  made  upon  test-pieces  turned  from  the  bars  to  a  reduced 
diameter,  which  at  one  point  was  reduced  by  a  groove  to  a 
much  less  one,  as  shown  in  Fig.  1,  p.  25. 


FORM  AND   PROPORTIONS   OF  TEST-PIECES. 


21 


The  errors  which  arise  through  the  use  of  this  erroneously 
shaped  and  proportioned  test-piece  have  been  frequently  pointed 
out,  first  by  Kirkaldy,  and  subsequently  by  C.  B.  Richards,  mem- 
ber American  Society  of  Civil  Engineers ;  but  it  does  not  ap- 
pear that  even  yet  the  errors  which  thus  arise  are  fully  recog- 
nized. As  a  case  in  point,  the  following  comparisons  of  the 
strength  of  various-sized  bars  of  iron  F,  as  found  by  our  tests, 
and  as  furnished  to  the  manufacturers  by  so-called  testers, 
will  fully,  illustrate. 

This  iron  is  alivays  of  so  uniform  a  strength  and  quality,  that 
the  test  of  one  bar  furnishes  most  valuable  evidence  as  to  the 
probable  strength  of  another. 

Strength  per  Square  Inch  of  Iron  F,  as  found  by  and  as  furnished  to  the 

Committee. 


IZE. 

No.  OF  TESTS. 

STRENGTH  FOUND. 

No.  OF  TESTS. 

STRENGTH  FURNISHED. 

DIFFERENCE 
IN  AVERAGES. 

Inches. 

From  — 

To  — 

Average 

From  — 

To  — 

Average 

| 

' 

3 
3 

Pounds. 

46,164 

47,558 

Pounds. 

46,702 

47,871 

Pounds. 

46,446 
47,764 

5 
4 
8 
18 
15 
15 
12 

Pounds. 

58,434 
54,759 
50,773 
58,111 
57,473 
59,440 
57,999 

Pounds. 

65,357 
60,757 
64,099 
71,025 
64,823 
67,471 
66,907 

Pounds. 

62,540 
57,236 
59,048 
63,586 
63,300 
63,350 
63,230 

16,094 
9,472 

13,963 
15,2i8 

3 

49,155 

49,465 

49,623 

9 

8 
8 
8 
8 
8 

46,862 
48,370 
48,792 
49,144 
49,342 
48,819 

49,700 
51,300 
50,342 
51,300 
51,840 
50,000 

48,132 
49,048 
50,325 
51,221 
51,423 
52,396 

12 

63,116 

75,545 

65,083 



66,312 

68,255 

67,062 



With  the  tabulated  statement  furnished,  the  average  tensile 
strength  of  all  sizes  combined  was  given  at  63,207  pounds ;  and 
the  results  from  the  sizes  If"  and  1§"  had  been  consolidated, 
also  those  from  li"  and  If". 

With  experimenters  developing  by  accident  such  a  uni- 
formity in  the  average  tensile  strength  of  the  various  sizes,  it 
is  not  to  be  wondered  at  that  no  attention  had  been  drawn  to 


22 


WROUGHT-IRON  AND   CHAIN-CABLES. 


the  variation  in  strength  accompanying  variations  in  diameter, 
which  is  plainly  indicated  in  our  more  correctly-made  experi- 
ments. 

The  broken  test-pieces  by  which  the  results  were  procured 
were  shown  to  us,  and  they  were  of  the  groove-form. 

We  determined  to  thoroughly  investigate  the  effect  upon  the 
results  which  were  due  to  variations  in  the  proportions  of  the 
test-pieces.  The  stock  of  contract-chain  on  hand,  all  of  which 
had  been  considered  to  be  of  a  tensile  strength  of  at  least 
60,000  pounds  per  square  inch  (the  standard  at  that  time,  as  it 
is,  or  was,  also,  of  the  British  navy),  furnished  material  for 
experiment ;  and  a  number  of  comparative  tests  were  made  by 
means  of  grooved  test-pieces  and  short  cylinders,  with  results 
as  follows :  — 

Comparison  of  Results  obtained  from  Chain-Iron  on  hand,  ly  means  of  Grooved 
Test-Pieces  and  Short  Turned  Cylinders. 


DIMENSIONS  OP 

Xo.  or 

TENSILE  STRENGTH  ^^V?,l™" 

TEST-PIECE. 

TESTS. 

PER  SQUARE  INCH. 

I;AAU   V^II^IIN- 
DERS  BY  — 

I 

j 

APPEARANCE  OP 

3 

2 

Jj 

E 

5 

E 

o 

00* 

. 

~c 

FRACTURE. 

J 

11 

| 

1 

1 

o 

5 

3 

i* 

1 

1 

o 

6" 

o 

0 

i.      Square  Inch. 

In. 

Pounds. 

Pounds. 

One-quarter. 

.20 

3 

3 

57,700 

71,530 

13,830 

23.5 

Fine  steely. 

Jg  One-quarter. 

.20 

2 

2 

56,600 

70,600 

14,000 

24.5 

Fine  steely. 

r    One-quarter. 

.20 

3 

2 

52,600 

65,850 

13,19024.0 

Fine  steely. 

*g  One-quarter. 

.20 

2 

2 

48,000 

59,000 

11,000 

25.0 

Fine  steely. 

One-quarter. 
6g  One-quarter. 

.20 
.20 

2 
2 

2 
2 

58,900 
52,400 

67,400 
62,800 

8,500 
10,400 

14.6 
20.0 

Coarse  granulous. 
Fibrous. 

j.    One-quarter. 

1.20 

o 

1 

54,200 

67,200 

13,000 

24.0 

Fibrous. 

One-quarter. 

1.20 

1 

.  . 

58,400 

67,200 

8,80015.0 

Coarse  fibre. 

7g  One-quarter. 

1.20 

2 

2 

46,900 

54,500 

7,60016.0 

Coarse  granulous. 

£  One-quarterJ,  1.20 

o 

2 

55,450 

65,400 

9,95018.0 

Gray  fibre. 

;    One-half.       ll.25 

2 

o 

54,300 

66,000 

11,70021.0 

Gray  fibre. 

9,  One-half. 

1.25 

2 

1 

58,400 

69,700 

11,300 

19.0 

Gray  fibre. 

One-half. 

1.25 

2 

1 

51,500 

64,900 

13,400 

26. 

Coarse  granulous. 

One-half. 

1.25 

o 

1 

50,900 

62,400 

11,500 

22. 

Coarse  granulous. 

§  One-half. 

1.25 

!o 
!•* 

1 

44,000 

58,500 

9,500 

19  1 

Coarse  granulous. 

.    One-half. 

1.25 

2 

1 

48,200 

56,900 

8,700 

18. 

Coarse  granulous. 

FORM  AND   PROPORTIONS   OF   TEST-PIECES. 


23 


These  results  made  it  evident  that  the  government  had  not 
received  iron  of  such  great  tensile  strength  as  was  supposed ; 
and  this  was  made  more  certain  by  the  results  procured  subse- 
quently by  comparative  tests  upon  several  of  the  irons  which 
make  up  our  records.  These  are  here  given.  One  groove-test 
was  made  upon  each  size. 

Comparison  of  Results  obtained  from  Cylindrical  and  from  Grooved  Test-Pieces. 
Irons  C,  B,  J,  F,  L,  E. 


DIMENSIONS 

.     ULTIMATE 

GrBOOVES   EX- 

IBON. 

OF  TEST- 

t 

STBENGTH  PEB 

CEED  CYLIN- 

PIECE. 

XI 

SQUABE  INCH. 

DEBS  BY  — 

h 

.« 

a 

. 

REMARKS. 

o  .. 

B 

• 

PH 

O 

• 

-/• 

a 

o 

"S  3 

!» 

§ 

"Si 

O 

C 

1 

6 

1 

3° 

s 

J 

1 

O 

~r 

6" 

1 

| 

In. 

In. 

In. 

Pounds. 

Pounds. 

C 

.864 

1.25 

2 

54,800 

47,885 

6,915 

14.5 

Strong  and  tough. 

C 

.864 

1.20 

2 

57,700 

48,600 

9,100 

10.8 

Hard  and  coarse. 

C 

.564 

1.30 

2 

58,900 

56,000 

2,900 

5 

Hard  and  coarse. 

C 

.564 

1.20 

2 

58,300 

52,000 

6,300 

12.1 

Hard  and  coarse. 

C 

.564 

1.25 

2 

59,100 

45,800 

13,300 

20 

Strong  and  tough. 

B 

Mi 

.800 

1.30 

2 

67,000 

51,900 

15,100 

29 

Strong,  good  stock. 

B 

41 

.800 

1.30 

2 

65,650 

53,600 

12,050 

22.5 

Not  enough  work. 

J 

If 

.800 

1.30 

2 

57,300 

50,350 

6,950 

14 

Irregular. 

J 

If 

.640 

1.40 

2 

62,200 

50,300 

11,900 

24 

Irregular. 

F 

If 

.800 

1.20 

2 

61,900 

50,130 

11,770 

23.5 

Soft  and  ductile. 

F 

H 

.564 

1.30 

2 

60,520 

50,400 

10,120 

20 

Soft  and  ductile. 

L 

Mi 

.800 

1.35 

2 

75,250 

58,390 

16,860 

29 

Steel. 

L 

If 

.564 

1.37 

2 

74,400 

59,290 

15,110 

25 

Steel. 

L 

it 

.670 

1.35 

2 

94,400 

75,233 

19,167 

25 

Steel. 

L 

.... 

.... 

1 



74,600 



26.5 

Steel. 

L 

1JL 

2 

80,000 

66,500 

13,500 

20 

Steel. 

E 

.800 

1.30 

2 

59,520 

50,080 

9,440 

18 

Tough  and  strong. 

E 

if 

.564 

1.30 

2 

61,060 

50,000 

11,060 

21 

Tough  and  strong. 

It  is  to  be  noticed  that  the  difference  between  the  results 
obtained  by  the  two  methods  is  greater  in  pure  refined  iron 
than  it  is  in  coarse  material.  A  single  experiment,  made  with 
a  test-piece  of  each  form  upon  cast-iron,  confirmed  this  view : 
the  difference  of  results  was  less  than  one  per  cent,  and  the 
cylinder  proved  that  much  the  stronger. 


24 


WROUGHT-IRON  AND   CHAIN-CABLES. 


A  series  of  experiments  was  undertaken  for  the  express  pur- 
pose of  enabling  us  to  decide  upon  the  correct  form  and 
proportions  necessary  in  the  test-pieces  to  insure  correct  results. 
The  first  of  this  series  was  made  upon  eighteen  test-pieces 
turned  from  a  2"  bar  of  a  remarkably  pure,  refined,  and  uniform 
iron  (K). 

No.  1  of  this  series  was  10"  long ;  and  the  length  decreased 
upon  each  successive  number,  until,  at  18,  the  groove-form  was 
reached.  The  diameters  were  nearly  constant,  except  in  two 
cases  where  seams  encountered  made  it  necessary  to  turn  away 
more  iron.  The  results  are  given  in  the  following  table :  — 

Iron  K. 


Number. 

Original 
Length. 

Per  Cent  of 
Elongation. 

Per  Cent  of 
Contraction 
of  Area. 

Stress  per 
Square  Inch 
when  Piece 
hegan  to 
Stretch. 

Breaking 
Stress  pei- 
Square  Inch. 

Remarks. 

Inches. 

Pounds. 

Pounds. 

1 

10 

23.1 

38.2 

29,678 

54,888 

Slight  seam. 

0 

9* 

243 

36.5 

28,011 

55,288 

3 

9 

21.5 

31.1 

29,345 

55,355 

4 
5 

8 

22 
25 

31.2 
39.9 

29,345 
30,840 

55,622 
54,890 

Slight  seam. 

6 

7 

25.8 

38.6 

30,412 

55,488 

7 

6£ 

22.1 

40.0 

28,562 

51,800 

Bad  seam. 

8 

6 

22.3 

34.7 

30,600 

55,418 

9 

5* 

25.4 

39.3 

29,475 

55,333 

10 

5 

21.2 

32.2 

29,278 

55,887 

Slight  seam. 

11 

4 

257 

37.4 

29,705 

55,5o2 

12 

3* 

26.7 

36.6 

31,817 

55,482 

13 

3 

27 

38.3 

31,123 

56,190 

14 

2 

27 

36.2 

33,428 

56,428 

Seamy. 

15 

H 

26 

34.0 

42,249 

57,096 

Seamy. 

16 

1 

37 

34.3 

34,288 

58,933 

17 

i 

30 

37.0 

57,565 

59,388 

Seamy. 

18 

Groove. 

.... 

20.6 

45,442 

71,300 

Nos.  13  and  18  of  the  preceding  table  are  reproduced  in  the 
following  illustration :  — 

Fig.  1  being  No.  18  of  the  table,  and  Fig.  2  No.  13 ; 
In  Fig.  1,  the  length  a  b  was  3",  the  diameter,  c  c,  .976". 
In  Fig.  2,  the  length  .a  b  was  3",  the  diameter,  c  c,  .970". 


FORM  AND   PEOPOBTIOXS   OF   TEST-PIECES. 


25 


The  pieces  were  nearly  the  same  in  dimensions ;  yet  the  stress 
at  which  No.  13  broke,  reduced  to  the  square  inch,  was  over 
fifteen  thousand  pounds  less  than  that  required  to  break  No.  18. 
This  difference  would  be  very  great  in  estimating  the  entire 
strength  of  the  bar  from  the  results  of  the  two  pieces.  Were 
those  from  No.  18  correct,  the  bar  would  be  equal  to  a  strain 
of  one  hundred  tons;  while  No.  13  shows  that  less  than 
seventy-nine  tons  would 
tear  it  asunder. 

By  the  table,  we  see 
that  the  piece  No.  13 
gave  higher  results  than 
those  which  were  long- 
er; the  average  tensile 
strength  developed  by 
Nos.  2,  3,  4,  6,  9,  10, 
11,  and  12  being  55,- 
488  pounds  per  square 
inch,  while  No.  13  gives 
56,190  pounds,  —  an  ex- 
cess of  751  pounds, — 
thus  suggesting  that  the 
length  of  this  piece,  viz., 
three  inches,  was  not  sufficient  to  insure  correct  results. 

No.  12  gives  a  result  much  closer  to  the  averages,  as  do  Nos. 
11  and  10. 

Assuming  that  the  proper  length  should  be  a  certain  percent- 
age of  the  diameter,  we  find  No.  13,  which  is  less  than  four 
diameters  in  length,  is  not  long  enough ;  No.  12,  of  about  four 
diameters,  gives  correct  results. 

The  preceding  tests  in  this  investigation  having  been  made 
upon  iron  with  considerable  tensile  strength,  it  was  thought 
advisable  to  make  one  more  experiment  with  a  bar  of  very  soft 
and  ductile  iron. 

A  two-inch  bar  was  selected,  which,  although  of  low  tensile 
strength,  was  very  tough  and  ductile. 


FIG.  1,  No.  18,  TABLE. 


FIG.  2,  No.  13,  TABLE. 


26 


WROUGHT-IKON  AND   CHAIN-CABLES. 


From  this  nine  test-pieces  were  turned,  of  lengths  from 
eight  inches  down,  to  the  groove-form,  each  successive  piece 
being  nearly  one  inch  shorter  than  its  predecessor,  and  all 
being  nearly  of  uniform  diameter.  They  were  tested  with  the 
following  results  :  — 

Iron  D. 


No. 

DIAMETER. 

ORIGINAL 
LENGTH. 

REDUCTION 
OF  AREA. 

PER  CENT 
ELONGA- 
TION. 

FIRST 
STRETCH 
PER  SQUARE 
INCH. 

ULTIMATE 
STRESS  PER 
SQUARE  INCH. 

Original. 

Fractured. 

1 
2 
3 
4 
5 
6 
7 
8 
9 

Inches. 

1.000 
.999 
1.000 
.999 
.998 
1.000 
1.001 
1.000 
.985 

Inches. 
.693 
.675 
.704 
.700 
.683 
.705 
.700 
.718 
.897 

Inches. 

8 
7 
5.82 
4.90 
3.95 
2.98 
1.98 
.975 
Groove. 

Per  Cent. 
52 
54.3 
50.3 
50.9 
53.1 
50.3 
51 
48.4 
17 

28 
29.8 
29.9 
31 
35 
36.1 
40.4 
45.2 

Pounds. 
28,619 
30,000 
26,700 
28,060 
26,588 

Pounds. 
45,800 
45,930 
45,995 
45,768 
46,561 
46,759 
46,734 
47,0:33 
61,023 

28,000 
28,200 
48,000 

The  results  indicate  that  with  iron  of  this  character  a  length 
equal  to  four  diameters  is  not  quite  sufficient  to  insure  accurate 
results. 

No.  5,  which  was  nearly  four  diameters  in  length,  gave  a 
tensile  strength  greater  by  689  pounds  per  square  inch  than 
was  developed  by  Nos.  1,  2,  3,  and  4,  which  were  very  uniform ; 
No.  4  being  five  diameters  in  length,  and  long  enough.  No.  6,  of 
three  diameters,  gave  still  higher  results ;  and  when  the  groove- 
form  was  reached  there  was  a  sudden  rise  of  over  13,000  pounds, 
a  difference  equal  to  33  per  cent  of  the  actual  strength. 

In  conclusion,  our  results  lead  us  to  the  decision,  that,  in 
testing  iron,  no  test-piece  should  be  less  than  one-half  inch  in 
diameter,  as  inaccuracy  is  more  probable  with  a  small  than  with 
a  large  piece,  and  the  errors  are  more  increased  by  reduction 
to  the  square  inch ;  that  the  length  should  not  be  less  than 
four  times  the  diameter  in  any  case ;  and  that,  with  soft  ductile 
metal,  five  or  six  diameters  would  be  preferable. 


COMPARATIVE  STRENGTH  OF  ROUGH  AND  TURNED  BARS.      27 

. 

These  rules  hold  good  in  testing  steel  also,  according  to  a 
number  of  results,  which  have  been  submitted  to  the  commit- 
tee, of  tests  made  upon  American  Bessemer  rail  steel ;  which 
results  are  confirmed  by  those  obtained  by  Col.  Wilmot  at  the 
Woolwich  Arsenal,  made  also  upon  Bessemer  steel,  which  we 
quote  as  follows :  — 

Material,  Bessemer  steel ;  test-pieces  of  one  square  inch  area. 

TENSILE   STRENGTH.  POUNDS  PER  SQUARE  INCH. 

By  groove  form  :  Highest 162,974 

Lowest .  136,490 

Average 153,677 

By  cylinder:  Highest 123,165 

Lowest 103,255 

Average 114,460 

The  grooved  thus  exceeding  the  cylinder  form,  32  to  34  per 
cent. 


PART  II. —COMPARATIVE  STRENGTH  OF  BARS  IN  THEIR 
NORMAL  CONDITION,  AND  AS  REDUCED  BY  TURNING 
AWAY  THE  SKIN  AND  ADJACENT  IRON. 

A  few  tests  were  made  by  tension ;  for  the  double  purpose  of 
ascertaining  if  the  strength  per  square  inch  of  iron  bars  with 
or  without  the  skin  is  the  same,  and  to  compare  the  results 
obtained  by  the  two  testing-machines  A  and  B.  The  following 
tables  show  some  of  the  results :  — 


28 


WEOUGHT-JBON  AND   CHAIN-CABLES. 


Consolidation  of  Results  from  226  Tests  "by  Tension  upon  Test-Pieces,  with  and 
without  Skin,  showing  Preponderance  of  Strength  in  Favor  of  the  Bar  in 
Normal  Condition. 


TESTIXG-MACHIXE  A. 


IRON. 

SIZE  or  BAB. 

No.  OF 
TESTS. 

TENSILE  STRENGTH  PER 
SQUARE  INCH. 

EXCESS  OF  STRENGTH. 

i 

Turned. 

Rough. 

Turned. 

Rough  over 
Turned. 

Turned  over 
Rough. 

[nches. 

Pounds. 

Pounds. 

Pounds. 

Pounds. 

D    .     .     .     . 

If 

i 

1 

51,499 

51,895 

.... 

396 

D    .     .     .     . 

1| 

i 

1 

51,127 

50,383 

744 

.... 

D    .     .     .     . 

11 

i 

1 

52,156 

53,347 

.... 

1,191 

D    .     .     .     . 

U 

i 

1 

51,275 

51,271 

4 

.... 

C    .     .    .     . 

2 

i 

1 

49,678 

49,735 

33 

.... 

C    .     .     .     . 

ii 

i 

1 

49,095 

48,726 

369 

.... 

C    .     .     .     . 

i 

1 

49,512 

51,367 

145 

.... 

C    .     .     .    . 

H1 

i 

1 

51,233 

49,419 

1,814 

.... 

E    .     .     .     . 

li 

i 

1 

51,739 

49,044 

2,695 

E    .     .     .     . 

I 

; 

i 

1 

51,606 

51,740 

'i34 

E    .     .     .     . 

1 

i 

1 

51,944 

50,844 

1,100 

.... 

E    .     .     .     . 

1_ 

i 

1 

55,411 

55,409 

o 

.... 

E    .     .     .     . 

1: 

i 

1 

52,255 

51,843 

412 

.... 

E    .     .     .     . 

1: 

i 

1 

53,894 

53,309 

585 

.... 

E    .     .     .     . 

i: 

i 

1 

53,098 

53,497 

.... 

399 

Hammered   . 

L 

- 

i 

1 

52,570 

52,424 

146 

.... 

Hammered   . 

1| 

i 

1 

56,818 

54,143 

2,675 

.... 

Hammered   . 

if 

2 

2 

57,280 

55,021 

2,259 

.... 

Hammered   . 

if 

1 

1 

55,542 

55,805 

.... 

203 

F    .     .     .     . 

1 

5 

1 

52,819 

52,810 

9 

.... 

F    .     .     .     . 

1. 

5 

1 

52,267 

51,675 

592 

.... 

F    .     .     .     . 

1 

5 

1 

52,620 

51,949 

671 

.... 

F    .     .     .     . 

1 

5 

1 

52,537 

50,403 

2,134 

.... 

F    .     .     .     . 

1. 

5 

1 

51,456 

50,799 

657 

.... 

F    .     .     .     . 

1- 

5 

1 

50,970 

49,605 

1,365 

.... 

F    .     .     .     . 

1 

5 

1 

49,738 

50,201 

.... 

463 

F    .     .     .     . 

H 

5 

1 

49,061 

49,682 

.... 

621 

F    .     .     .     . 

2 

5 

1 

47,569 

48,170 

.... 

601 

F    .     .     .     . 

24 

2 

2 

48,505 

49,164 

.... 

659 

F    .     .     .     . 

2f 

2 

2 

47,344 

48,475 



1,131 

69 

33 

COMPARATIVE  STRENGTH  OF  ROUGH  AND  TURNED  BARS.      29 


TESTIXG-MACHINE  B. 


IRON. 

SIZE  OF  BAR. 

No.  or 

TESTS. 

TENSILE  STRENGTH  PER 
SQUARE  INCH. 

EXCESS  OF  STRENGTH. 

ja 

6C 
I 

Turned. 

Rough. 

Turned. 

Rough  over 
Turned. 

Turned  over 
Rough. 

Inches. 

Pounds. 

Pounds. 

Pounds. 

Pounds. 

c 

i* 

4 

3 

52,949 

52,796 

153 

.... 

c 

i 

3 

3 

54,076 

52,475 

1,601 

.... 

c 

i 

6 

5 

55,725 

55,311 

414 

.... 

c 

i 

8 

6 

57,846 

62,813 

•  ... 

4,967 

D 

1 

6 

4 

53,400 

52,408 

992 

.... 

K 

i 

3 

3 

62,269 

60,536 

1,733 

«... 

K 

i 

4 

3 

61,945 

62,156 

.... 

211 

Contract  iron 

I 

3 

4 

60,466 

59,696 

770 

.... 

F,  first  lot 

i 

4 

4 

52,155 

51,547 

608 

.... 

F,  first  lot 

i 

3 

3 

52,645 

51,540 

1,105 

.... 

F,  first  lot 

1 

6 

5 

57,257 

57,668 

.... 

411 

F,  first  lot 

1 

G 

5 

55,644 

54,964 

680 

.... 

F,  third  lot 

3 

1 

50,716 

50,374 

342 

.... 

j  , 

3 

1 

51,969 

50,276 

693 

.... 

3 

1 

52,032 

51,431 

601 

.... 

3 

1 

53,755 

52,775 

980 

.... 

3 

1 

71 

53 

In  case  of  the  half-inch  bars  of  iron  C,  of  which  the  turned  so 
greatly  exceeded  the  rough  in  strength,  there  is  some  reason  to 
suspect  that  a  piece  of  the  bar  of  iron  K  was  by  mistake  sub- 
stituted for  that  of  C.  In  case  of  iron  K,  where  the  turned 
exceeded  the  rough  bar,  the  threads  of  the  latter  stripped. 

The  accumulated  evidence  indicates  that  the  strength  of  the 
skin  of  the  bar  is  greater  in  proportion  to  its  area  than  that  of 
the  rest  of  the  bar. 

In  making  the  foregoing  tests,  we  find  that  in  sixteen  com- 
parative tests  of  small  bars  by  testing-machine  B,  and  in  thirty 
comparative  tests  upon  larger  bars  by  testing-machine  A,  mak- 
ing forty-six  in  all,  in  thirteen  cases  of  the  former  and  twenty 
of  the  latter,  thirty-three,  or  over  72  per  cent,  the  excess  of 
strength  occurred  with  bars  in  their  normal  condition. 


30  TVKOUGHT-IBON  AND   CHAIN-CABLES. 

With  iron  F,  which  was  so  uniform  in  its  structure  that  any 
peculiarity  which  manifested  itself  by  any  particular  test  seemed 
to  indicate  a  possible  law,  we  find  that,  with  the  bars  which 
received  the  most  work,  viz.,  from  V  to  If"  inclusive,  the  rough 
bars  were  stronger  than  the  turned;  above  If" the  more  slightly- 
worked  sizes  reversed  the  proportion.  If  this  result  can  be 
accepted  as  indicative,  it  would  be  wise,  in  estimating  the  entire 
strength  of  a  large  bar  by  the  data  afforded  by  the  test  of  a 
cylinder  turned  from  its  centre,  to,  as  has  already  been  said, 
consider  it  probable  that  an  over-estimate  would  be  made.  For 
instance,  the  strength  of  the  2J"  bar  was  192,861  pounds  by 
actual  test  of  the  entire  bar ;  by  test  of  turned  bar,  195,481 
pounds ;  by  test  of  cylinder,  195,981  pounds ;  showing  a  possible 
over-estimate  of  3,120  pounds  by  use  of  cylinder  turned  from 
the  core. 


TESTS   OF  BARS   BY  IMPACT.  31 


SECTION   III. 

Tests  of  Bars  by  Impact;  showing  Action  of  Various   Types  of  Iron  under 

Sudden  Strains. 

THE  tests  by  which  we  have  ascertained  the  powers  of  the 
various  irons  of  the  series  to  resist  steady  tensional  strains* 
applied  in  the  direction  of  the  fibre,  and  when  manufactured 
into  links,  have  furnished  us  with  no  data  by  which  their  rela- 
tive powers  to  resist  sudden  strains,  applied  transversely,  could 
be  judged.  As  cables  are  more  frequently  broken  by  strains 
of  this  nature  than  by  all  other  causes  combined,  it  was  con- 
sidered to  be  absolutely  necessary  that  the  series  should  be 
subjected  to  such  tests  as  would  develop  their  relative  values 
in  this  respect  before  we  could  express  an  opinion  as  to  which 
of  the  varying  characteristics,  as  developed  by  tension  alone, 
indicated  that  the  iron  in  which  they  existed  could  be  con- 
sidered as  in  every  way  suitable  for  the  manufacture  of 
cables. 

Having  no  apparatus  by  which  such  tests  could  be  made, 
one  was  devised  by  the  chairman  of  the  committee,  by  the 
use  of  which  we  were  enabled  to  form  a  fair  judgment  as 
to  the  comparative  values  of  the  irons  when  subjected  to 
shocks. 

The  following  is  a  description  of  this  machine,  which  was 
known  as  the  "  impact  hammer :  "  — 

The  Impact  Hammer.  —  A  cast-iron  hammer  having  a  wedge- 
shaped  impact  surface  upon  its  lower  side  is  made  to  transverse 
two  perpendicular  iron  rods  of  say  2J  inches  diameter  and  from 


32  WEOUGHT-IRON   AND   CHAIN-CABLES. 

SO  to  50  feet  in  length,  which  pass  through  holes  in  the  body 
of  the  hammer.  The  hammer  may  be  of  any  weight,  a  con- 
venient one  being  100  pounds.  A  traveller  of  wood  or  metal, 
fitted  with  a  pair  of  hooks  which  can  be  opened  or  closed  by 
pulling  up  a  cord  attached  to  them,  is  placed  upon  the  rods 
above  the  hammer.  At  the  foot  of  the  rods,  they  passing 
through  it,  is  fitted  a  cast-iron  block  with  a  cylindrical  opening 
eight  inches  in  diameter.  The  specimen  of  iron  to  be  tested 
is  placed  across  this  circular  hole,  the  hammer  resting  upon  the 
box  which  surrounds  the  anvil  and  supported  by  a  chock,  to 
prevent  accidents.  A  common  purchase,  through  which  a  hoist- 
ing-rope is  led  to  the  windlass,  is  secured  to  the  portion  of  the 
framework.  At  the  side  of  one  of  the  rods  an  upright,  marked 
plainly  in  feet  and  inches,  is  secured. 

To  use  the  machine,  the  hammer  is  hoisted  to  the  desired 
height,  the  lower  edge  of  the  hammer  being  brought  in  line 
with  the  figure  on  the  measuring-rod.  When  at  the  proper 
height,  the  tripping-line  is  pulled,  opening  the  hooks,  and  re- 
leasing the  hammer,  which  falls,  striking  the  specimen  in  the 
centre  a  blow  whose  force  can  be  measured,  and  which  is  de- 
pendent upon  the  force  of  gravity  at  the  location,  and  slightly 
diminished  by  friction. 

METHOD  OF  TESTING  BY  IMPACT. 

Our  method  of  testing  by  this  machine  was  this :  Test-pieces, 
not  less  than  twelve  diameters  in  length,  were  placed  across 
the  hole  through  the  anvil,  the  centres  being  directly  under  the 
edge  of  the  wedge-shaped  hammer,  which  was  raised  to  various 
heights,  and  allowed  to  drop  upon  them. 

Bars  of  some  irons  which  were  tested  by  this  method  could, 
while  in  their  normal  condition,  the  skin  being  in  no  manner 
nicked  or  weakened,  be  broken  by  two  blows  of  less  than  three 
thousand  foot-pounds  force ;  with  other  irons  it  was  necessary 
to  weaken  them  by  a  circular  score  ^  of  an  inch  deep,  that 
we  might  succeed  in  breaking  the  test-piece,  it  not  being  con- 
venient to  use  a  hammer  over  one  hundred  pounds  weight. 


TESTS   OF  BAES  BY  IMPACT.  33 

which  could  be  hoisted  but  thirty  feet.  This  cut  through  the 
skin  reduced  the  bar's  power  to  resist,  in  the  same  manner  that 
it  is  reduced  by  the  ordinary  method  of  nicking  with  a  cold- 
chisel,  and  the  blows  of  the  hammer  were  of  the  same  nature 
as  those  given  by  sledge-hammers ;  but  with  this  machine  the 
force  of  the  blow  could -be  regulated  and  known,  and  the 
weakening  produced  by  the  cuts  made  uniform. 

The  wedge-shaped  portion  of  the  hammer  permitted  a  bar  to 
bend  to  an  angle  of  120.° 

Through  the  data  collected  by  the  test,  by  this  method, 
of  a  large  number  of  bars  of  various  irons  differing  widely  in 
character,  we  were  able  to  detect  the  existence  of  a  connecting 
link,  and  partially  trace  its  course,  between  the  characteristics 
displayed  under  tension,  and  those  produced  by  impact. 

Iron  with  high  tensile  strength  generally  proved  to  be  pos- 
sessed of  .  but  comparatively  low  resilience ;  it  would  break 
under  the  blows  with  but  slight  deflection,  arid  leave  a  fractured 
surface,  smooth  as  though  the  bar  had  been  cut  in  two  by  a 
sharp  knife,  the  ends  of  the  fibres  showing,  like  steel,  a  fine, 
slightly  granulous  surface. 

Iron  of  coarse,  slightly-worked  character  would  have  an 
equally  smooth  and  bright  surface,  but  the  coarse,  granulous 
appearance  of  the  cut  fibres  denoted  how  slightly  they  had 
been  affected  by  the  rolls. 

Iron  with  a  high  elastic  limit  would  resist  the  first  blow,  with 
but  little  injury  or  deflection ;  but,  the  deflection  once  started 
by  subsequent  blows,  it  would  yield  more  at  each  than  would 
other  irons  with  a  lower  limit,  which  were  more  affected  by  the 
first  blow.  Some  irons  would,  after  having  been  weakened  by 
the  circular  cut  through  the  skin,  resist,  with  slight  injury, 
blows  which  would  break  in  two  bars  of  the  same  size  of  other 
irons  which  had  not  been  so  weakened. 

There  are  many  irons,  valuable  for  many  purposes,  which 
would  not  yield  good  results  under  this  form  of  test;  but, 
however  valuable  for  other  purposes,  the  material  which  proves 
brittle  under  test  cannot  be  expected,  when  made  into  cable, 


34  WKOUGHT-LRON  AND   CHAIN-CABLES. 

and  subjected  to  strains  of  a  similar  nature,  to  prove  equal  to 
its  tasks. 

Iron  which  is  materially  weakened  by  a  repetition  of  slight, 
sudden  strains,  none  of  which  produce  perceptible  injury,  but 
which  do  so  injure  it  that  eventually  a  strain  no  greater,  and 
perhaps  much  less,  than  those  previously  encountered,  will 
destroy  it,  is  not  suitable  for  cable.  Iron  whose  entire  strength 
depends  upon  its  remaining  perfectly  free  from  abrasion,  or 
slight  cracks,  is  not  suitable  for  cables.  Our  tests  by  impact 
revealed  that  large  quantities  of  iron  possessing  the  above 
defects  had  been  accumulated  by  the  government,  all  having 
passed  satisfactorily  the  examinations,  which  consisted  of 
tension  tests  made  upon  test-pieces  of  erroneous  proportions. 
Much  of  this  iron  was  of  good  material ;  but  the  low  price  at 
which  it  had  to  be  supplied,  in  order  that  the  lowest  bidder 
should,  as  the  law  directed,  receive  the  contract,  had  neces- 
sitated, that,  in  order  to  make  it  cheap  enough,  but  very  little 
work  should  be  expended  upon  it. 

Our  experiments  demonstrated  not  only  its  want  of  value  in 
its  present  state,  but  also  that  by  thorough  work  it  could  be 
vastly  improved ; ,  and  when,  in  addition  to  this  work,  material 
of  no  greater  cost,  but  possessing  qualities  that  the  coarse 
chain-iron  lacked,  was  added,  we  found  that  most  valuable 
iron,  capable  of  resisting  all  strains,  was  produced. 

An  example  of  such  a  transformation  will  be  described: 
The  material  selected  was  taken  from  the  pile  of  2TV'  cnain- 
iron,  and  was  probably  as  inferior  a  bar  of  iron  as  could  be 
found  in  the  pile,  or  in  our  markets,  there  being  in  the  stock  of 
chain-iron,  however,  a  great  many  equally  poor. 

These  bolts,  each  over  26"  long,  were  thoroughly  tested. 
Several  which  had  not  been  weakened  by  a  score  were  broken 
square  in  'two  by  a  single  blow  of  the  hammer  dropped  twenty- 
five  to  thirty  feet;  others,  having  been  struck  from  ten  to 
twenty  times  by  the  hammer,  from  a  height  of  eight  or  ten 
feet,  and  showing  no  injury  or  deflection,  would,  upon  receiving 
another  blow  of  no  greater  force,  break  in  two;  other  bars, 


TESTS   OF  BARS   BY  IMPACT.  35 

scored  as  has  been  described,  would  break  in  two  at  single 
blows  of  from  one  to  three  feet  drop. 

In  all  cases,  the  appearance  of  the  fracture  was  the  same, 
and  would  be  described  as  "  bright,  coarse,  granulous." 

Iron  from  this  lot,  having  been  first  thoroughly  re-worked, 
was  piled  with  alternate  layers  of  old  boiler-iron,  and  hammered 
into  a  bloom,  from  which  a  bar  of  2"  diameter  was  swaged. 
This  was  cut  into  pieces  24"  long,  and  the  pieces  were  scored 
in  two  places,  8"  apart,  and  then  tested  as  was  the  original 
bar,  except  that  each  drop  of  the  hammer  was  from  a  height 
of  thirty  feet.  The  first  score  received  ten  such  blows  before  it 
was  entirely  torn  in  two,  and  the  fractured  surface  appeared 
fibrous. 

The  extreme  difference  between  the  appearance  of  fractures 
made  upon  the  same  material  (and  it  of  great  resisting  powers), 
by  different  degrees  of  the  same  force,  indicates  that  it  is  unsafe, 
even  for  an  expert,  to  attempt  to  give  evidence  as  to  the  char- 
acter of  the  material  from  which  a  bridge,  axle,  or  cable,  that 
has  been  accidentally  broken,  was  made,  unless  he  knows  just 
Jioiv  it  was  broken.  To  render  a  judgment  upon  this  point,  a 
person  must  not  only  be  an  expert,  but  he  must  know  by  what 
character  and  amount  of  force  the  fracture  was  produced. 

The  fractures  illustrated  in  the  frontispiece,  Fig.  2,  supply 
evidence  of  this  fact.  The  three  were  made  by  impact  upon 
the  same  bar  (of  iron  A,  li"  diameter)  which  was  scored  in 
three  places,  eight  inches  apart.  At  a  the  score  was  slight,  and 
the  piece  was  torn  in  two  by  repeated  light  blows. 

At  b  the  score  was  the  same ;  but,  after  the  bar  had  been 
broken  half  in  two  by  light  blows,  one  heavy  one  was  given, 
which  cut  in  two  the  remainder. 

At  c  the  score  was  deep,  and  one  heavy  blow  did  the  work  : 
a  would  be  described  as  "  all  fibrous,"  b  as  "  half  granulous  and 
half  fibrous,"  c  as  "  bright  granulous." 

Irons  F,  Fx,  O,  D,  H,  G,  Px,  and  some  of  the  bars  of  B,  C, 
and  P,  resemble  more  or  less  in  their  characteristics  the  iron 
shown  in  this  plate. 


36  WROUGHT-IKOX  AND  CHAIN-CABLES. 

BAEKING. 

A  peculiar  phenomenon  occurred  with  irons  of  a  certain  type, 
during  the  test  by  impact,  which  was  given  the  shop  name  of 
"barking."  The  illustration  in  frontispiece,  Fig.  1,  will  give 
a  clearer  idea  than  description  can  of  this  phenomenon.  This 
occurred  only  in  tests  of  very  tough,  ductile  iron  which  had  been 
thoroughly  worked,  and  which  required  several  repetitions  of 
the  blows  to  break  in  two. 

As  the  deflection  caused  by  each  successive  blow  increased, 
the  transverse  crack  at  the  lower  part  of  the  test-piece  widened, 
and  the  surface  iron  became  detached,  and  stood  open  like  a 
detached  bark.  A  tough  gray  ligature  with  splintered  surface 
connected  the  two  ends,  and  a  finger  could  be  thrust  under  the 
skin  on  either  side. 

Several  photographs  were  made  of  instances  of  this  action  ;  it 
being  deemed  peculiar  to  most  excellent  iron,  occurring  only 
with  A,  C,  F,  Fx,  and  6. 

CRYSTALLIZATION. 

The  question  as  to  whether  crystallization  can  be  produced  in 
iron  by  stress,  or  by  repetition  of  stress  with  alternations  of 
rest,  or  by  vibration,  has  been  much  discussed,  and  very  oppo- 
site views  are  entertained  by  experts. 

We  have  met  but  with  one  unmistakable  instance  of  crystal- 
lization which  was  probably  produced  by  alternations  of  severe 
stress,  sudden  strains,  recoils,  and  rest. 

The  connecting-rod  of  the  chaiu-prover  was  five  inches  in 
diameter,  and  had  been  in  use  for  forty  years,  and  had,  during 
this  period,  been  frequently  subjected  to  stress  up  to  250,000 
pounds,  with  recoils  produced  by  rupture  of  test  pieces. 

It  was  carefully  made  in  the  anchor-shop,  being  hammered 
from  the  best  quality  of  wrought-iron  scrap.  It  is  not  probable 
than  any  section  of  it,  if  broken  when  first  made,  would  have 
displayed  crystalline  structure ;  but,  while  we  were  testing,  it 
parted  one  day  at  less  than  200,000  pounds  stress,  and  the 


TESTS   OF  BAKS  BY  IMPACT.  87 

surface  of  the  fractured  ends  showed  well-defined  crystalliza- 
tion, the  facets  being  large  and  bright  as  mica.  •  The  ends  hav- 
ing become  injured  by  rust,  the  bar  was  again  broken  by  impact 
at  a  point  distant  over  a  foot  from  the  first  fracture,  and  the 
same  appearance  was  found.  The  original  of  this  fracture  is 
now  in  the  cabinet  of  Stevens  Institute  of  Technology. 

IMPACT  TESTS. 

The  records  of  tests  by  impact  begin  with  the  history  of  an 
examination  made  upon  the  contract  chain-iron  in  store,  made 
by  the  chairman  of  these  committees,  acting  under  the  instruc- 
tions of  the  Navy  Department,  with  the  object  of  ascertaining 
the  character  of  the  iron  on  hand,  and  the  effect  of  thorough 
re-working  upon  such  as  was  found  unsuitable  for  cables. 

This  iron  was  stowed  in  piles  classified  by  diameters.  Most 
of  it  had  been  received  during  the  war  from  such  contractors 
as  had  bid  lowest,  and  its  origin  beyond  this  point  was  unknown : 
its  general  character,  as  found  by  this  examination,  was  worth- 
less in  its  present  state.  The  results  of  the  experiments  in 
re-working,  and  in  combining  it  with  scrap-iron  of  a  superior 
quality,  were  such  that  the  iron  produced  was  pronounced  by 
the -Chief  of  the  Bureau  of  Steam  Engineering  as  "at  least 
equal,  if  not  superior,  to  the  best  commercial  iron,  at  less  cost." 

[The  original  report  contains  the  records  of  about  a  thousand 
impact  tests.  From  these  the  abridger  has  selected  the  records 
of  irons  F  and  M,  as  showing  the  variation  of  resistance  to 
impact  between  a  soft,  ductile  iron,  and  a  hard,  brittle  iron.] 


38 


WEOUGHT-IROX  AND   CHAIN-CABLES. 


Record  of  Tests  by  Impact. 

IRON  F.  —  UNSCORED. 

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TESTS   OF  BAES  BY  IMPACT. 


39 


IKON  M.  —  TINS  CORED. 


DIAMETER. 

FORCE  AXD  EFFECT  OF  BLOWS. 

REMARKS. 

FIRST. 

SECOND. 

THIRD. 

Force, 
Foot-pounds. 

Eftect  and 
Deflection. 

Force, 
Foot-pounds. 

Eftect  and 
Deflection. 

Force, 
Foot-pounds. 

Eftect  and 
Deflection. 

j' 

2 

11 
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13 
13 
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If 
ll 

li 
if 
lg 
li 
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ii 
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if 
if 

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2,500 
2,000 
2,000 
2,200 
2,000 
1,500 
1,500 
1,600 
1,700 

1,000 
1,200 
1,000 
800 
600 
500 
400 
600 
500 

D 
D 

a 
c 
c 

F 

D 
C 
C 

D 
D 

C 

D 
D 
D 
F 
C 
C 
D 
T 

All  bright  granulous. 
All  bright  granulous. 
All  bright  granulous. 
All  bright  granulous. 
90  per  cent  bright  granuloue. 
90  per  cent  bright  granulous. 
80  per  cent  bright;  the  rest  dark  and  dull. 

80  per  cent  bright;  the  rest  dull,  short  fibre. 

About   equally  mixed,  dark   short  fibre,  and  bright 
granulous. 

All  bright  granulous;  very  short. 
90  per  cent  bright  granulous  ;  very  short. 
Bright  granulous  ;  very  short. 

90  per  cent  bright  ;  the  rest  dull  fibre  on  one  side. 
90  per  cent  bright  granulous. 
Mixed  dull  fibre  and  bright  granulous. 
End  just  hanging  on  by  small  bit  of  fibre;   the  rest 
bright  granulous. 

.... 

•• 

.... 

• 

500 
1,000 

D 
D 

!!!.' 

.. 

500 
300 

D 
F 

'.'.'.. 

•• 

1,000 

+ 

600 

F 

300 
400 

F 

+ 

'466 

F 

Explanation  of  Symbols  used  in  the  above  Tables. 

The  figures  under  "  effect  and  deflection  "  are  deflections  in  degrees,  from  horizontal. 

"  B.C.,"  a  slight  crack  in  which  a  needle-point  could  be  inserted,  and 

"  C.,"  a  crack  wide  and  deep  enough  to  insert  the  edge  of  a  knife. 

"  +,"  an  increase  in  the  opening,  but  not  enough  to  term 

"  B.C.,"  a  bad  crack. 

"  F.,"  a  fracture  in  which  the  ends  are  torn  apart,  leaving  long,  jagged  splinters. 

"  JjF.,"  an  incomplete  fracture  of  the  same  nature,  the  ends  still  remaining  connected. 

"  D,"  a  short  square  break,  with  little  or  no  deflection,  the  fractured  surfaces  showing  smooth 
as  if  cut  in  two. 

"  Closed  to  hammer,"  the  test-piece  is  bent  to  from  110°  to  120°,  and  in  contact  with  the  face  of 
the  wedge  of  the  hammer. 

"  Closed  down,"  the  piece  has  been  still  further  closed  under  the  steam  hammer,  until  the 
sides  are  in  contact  the  whole  length. 


40  WEOUGHT-IEOX   AXD   CHAIX-CABLES. 


SECTION  IY. 

A  Paper  describing  a  Series  of  Experiments  to  determine  Facts  in  regard  to  the 
Operation  of  the  Law  called  the  Elevation  of  the  Limit  of  Stress. 

THE  discovery  that  wrought-iron,  after  having  been  subject- 
ed to  a  steady  stress  up  to  the  point  of  its  ultimate  strength, 
would,  if  then  released  from  stress  and  permitted  to  rest,  expe- 
rience an  elevation  in  both  its  elastic  and  tensile  limit,  was  made 
by  Professor  Robert  H.  Thurston  in  November,  1873,  and  by 
the  chairman  of  these  committees  a  short  time  afterward,  while 
carrying  on  an  investigation  by  tension,  Professor  Thurston 
having  made  his  discovery  by  torsion  tests.  The  discoveries 
were  entirely  independent,  neither  experimenter  having  any 
knowledge  of  the  other's  work. 

As,  at  the  beginning  of  the  series  of  tests  incorporated  in  this 
report,  but  little  data  had  been  obtained  as  to  the  operation  of 
this  new  law,  it  was  thought  worth  while,  while  making  investi- 
gations in  regard  to  chain-iron,  to  utilize  at  slight  expense  many 
of  the  test-pieces,  in  investigating  its  action.  By  bringing  a 
test-piece  to  the  tensile  limit,  all  data  as  to  its  strength  are 
obtained ;  and  by  carrying  the  test  to  rupture,  we  gain  simply 
the  dimensions  after  rupture,  and  means  to  reduce  the  strength, 
&c.,  to  those  measurements. 

We  therefore  released  a  number  of  test-pieces  from  stress, 
when  the  tensile  limit  was  reached,  and,  preserving  them  for 
various  periods,  eventually  broke  them,  with  results  as  given  in 
the  following  paper :  — 


ELEVATION  OF  THE  LIMIT  OF  STKESS.  41 

ELEVATION  OF  THE  LIMIT  OF  THE  STEESS. 

Experiments  Nos.  1  to  10. 

Twelve  test-pieces  which  had  been  strained  to  the  point  of 
"  tensile  limit "  while  testing  irons  C,  D,  and  K,  were  permitted 
to  rest  free  from  strain  for  from  twenty-four  to  thirty  hours, 
then  broken  with  results  as  follows :  — 

No.  1.  Iron  C,  2" ;  strength  second  day  over  that  at  first  test, 
3,357  pounds  per  square  inch,  or  6.6  per  cent. 

No.  2.  Iron  C,  1J";  strength  second  day  over  that  at  first  test, 
2,238  pounds  per  square  inch,  or  4.4  per  cent. 

No.  3.  Iron  C,  1J";  strength  second  day  over  that  at  first  test, 
7,506  pounds  per  square  inch,  or  15.1  per  cent. 

No.  4.  Iron  C,  1J";  strength  second  day  over  that  at  first  test, 
8,560  pounds  per  square  inch,  or  17  per  cent. 

No.  5.  Iron  D,  2" ;  strength  second  day  over  that  at  first  test, 
952  pounds  per  square  inch,  or  2  per  cent. 

No.  6.  Iron  D,  1J";  strength  second  day  over  that  at  first  test, 
7,354  pounds  per  square  inch,  or  15.7  per  cent. 

No.  7.  Iron  D,  If";  strength  second  day  over  that  at  first  test, 
7,773  pounds  per  square  inch,  or  16.1  per  cent. 

No.  8.  Iron  D,  1|";  strength  second  day  over  that  at  first  test, 
8,605  pounds  per  square  inch,  or  16.7  per  cent. 

No.  9.  Iron  D,  1J";  strength  second  day  over  that  at  first  test, 
6,904  pounds  per  square  inch,  or  14.1  per  cent. 

No.  10.  Iron  D,  1J";  strength  second  day  over  that  at  first 
test,  8,325  pounds  per  square  inch,  or  16.3  per  cent. 

No.  11.  Iron  K,  1|";  strength  second  day  over  that  at  first 
test,  4,203  pounds  per  square  inch,  or  8.2  per  cent. 

No.  12.  Iron  K,  1";  strength  second  day  over  that  at  first 
test,  5,040  pounds  per  square  inch,  or  8.8  per  cent. 

Nos.  11  and  12  were  of  a  fine,  strong  iron,  with  considerable 
carbon,  breaking  with  a  steel-like  fracture :  the  remainder  were 
all  from  tough,  fibrous  iron.  The  indications  were  that  the  lat- 
ter type  of  iron  gained  the  most  by  the  rest.  While  testing 


42  WKOUGHT-IKON  AND  CHAIN-CABLES. 

the  foregoing  pieces,  the  stress  which  produced  the  first  per- 
ceptible elongation  (about  .002  of  an  inch)  was  observed ;  and 
on  the  first  test  this  stress  was  from  61  to  70,  averaging  about 
65  per  cent  of  the  ultimate  strength.  Upon  testing  them  the 
second  time,  the  stress  which  produced  first  stretch  was  nearly 
identical  with  the  ultimate  strength. 

Second  Experiment.  —  Forty-two  test-pieces  of  iron  F,  which 
was  of  remarkably  uniform  structure,  were,  after  having  been 
strained  to  "  tensile  limit,"  allowed  to  rest  for  periods  varying 
from  one  minute  to  six  months,  when  they  were  re-tested  with 
results  as  per  table. 

Elevation  of  the  Limit  of  Stress.     Iron  F.     Abstract  from  Detail  of  Tests. 

PER  CENT.       TESTS. 

Average  gain  in  less  than  one  hour  .  .  .1.1  5 
Average  gain  in  less  than  eight  and  over  one  hour,  3.8  8 
Average  gain  in  three  days  .  .  .  .16.2  10 
Average  gain  in  eight  days  .  .  .  .17.8  2 
Average  gain  in  over  eight  and  less  than  forty- 
three  days 15.3  5 

Average  gain  in  six  months        ....     17.9  12 

42 

The  elongation  was  irregular ;  that  of  those  broken  at  first 
stress  and  of  those  after  six  months'  rest  coinciding  at  29  per 
cent,  while  intermediates  varied  from  27.5  per  cent  to  30  per 
cent. 

Having  failed  to  procure  data  as  to  the  effect  of  rest  after 
strain,  for  periods  between  eight  hours  and  three  days,  it  was 
resolved  to  fill  the  hiatus  with  a  series  made  upon  iron  D,  which 
resembled  iron  F,  except  in  possessing  somewhat  greater  te- 
nacity when  tested  as  an  entire  bar. 

Seven  test-pieces  were  brought  to  tensile  limit  upon  one  day, 
and  broken  after  twenty-four  hours  of  rest,  with  an  average 
gain  of  15.4  per  cent.  This  is  but  slightly  below  that  of  the 
pieces  of  iron  F  rested  three  days  (16.2  per  cent)  ;  and  we  may 
consider  that  at  the  end  of  one  day  the  result  is,  with  very 
ductile  irons,  practically  accomplished. 


ELEVATION   OF  THE  LIMIT   OF   STRESS. 


43 


Reduction  of  Strength  letiveen  the  Ultimate  reached,  and 
Breaking-point. 

Six  of  the  forty-two  pieces  were,  after  reaching  the  tensile 
limit,  on  the ;  second  test,  still  further  tested  thus :  The  lever 
having  fallen,  weights  were  removed  until  a  balance  took  place, 
which  balance  was  maintained  by  removal  of  weights  while  the 
crank  was  turned  without  cessation,  but  slowly ;  and  the  speci- 
mens finally  ruptured  at  strains  considerably  less  than  the 
original  strength,  thus:  — 


INTERVAL,  BETWEEN  FIRST 
AND  SECOND  TESTS. 

ORIGINAL 

STRENGTH. 

STRENGTH  AT 
RUPTURE. 

Loss. 

Pounds. 

Per  Cent. 

1  hour      

Pounds. 

49,345 
49,358 
49,401 
49,206 
50,257 
50,313 

Pounds. 
42,952 
43,049 
42,271 
42,364 
42,914 
43,121 

6,393 
6,309 
7,130 
6,842 
7,343 
7,192 

12.9 
12.9 
14.4 
13.9 
14.5 
14.2 

2  hours 

3      "                       .     . 

4      «        

5      "        

6      "                        .     . 

Average  .... 

6,868 

13.8 

Percentage  of  Change  of  Form  at  Tensile  Limit  to  that  at 

Fracture. 

At  tensile  limit  the  average  reduction  of  area  which  had 
taken  place  was  equal  to  53  per  cent  of  that  at  rupture,  and  the 
average  percentage  of  elongation  was  80  per  cent. 

The  average  of  the  same  percentages  upon  the  twenty-three 
pieces  broken  by  single  continued  strain  was,  of  reduction  of 
area,  49  per  cent ;  of  elongation,  78  ^>er  cent; :  from  which  aver- 
ages we  deduce,  that,  at  the  instant  of  ceasing  to  resist  an  in- 
crease of  stress,  the  reduction  of  area  which  has  taken  place 
is  about  one-half,  and  of  elongation  a  little  over  three-quarters, 
of  that  which  will  have  occurred  if  the  metal  be  further 


44  WBOUGHT-IKON  AND  CHAIN-CABLES. 

strained  to  rupture.  This,  we  believe,  will  not  prove  true  if  the 
metal  is  ruptured  by  a  sudden  strain,  by  the  action  of  which 
the  fractured  dimensions  will  nearly  coincide  with  those  which 
would  have  existed  at  tensile  limit  had  the  piece  been  broken 
by  steady  strains.  This  was  indicated  by  the  results  of  an  ex- 
periment with  an  apparatus  which  we  devised,  by  which  we  were 
enabled  to  apply  sudden  strains  to  the  specimen. 

By  means  of  a  pair  of  spring  clamps,  a  holder  was  attached 
to  the  upper  and  lower  clamps  of  tlie  dynamometer ;  and  the 
stress  produced  by  turning  the  crank,  or  some  indefinite  por- 
tion of  it,  was  accumulated  in  the  legs  of  this  holder,  and  at 
will  transferred  suddenly  to  the  specimen.  The  machine  was 
imperfect,  its  use  involved  risk  of  injury  to  the  dynamometer, 
and  we  made  but  one  test  with  it,  which  was  as  follows :  — 

Comparison  of  Effect  of  Steady  and  Sudden  Strains  upon  Change 

of  Form. 

Two  specimens  of  nearly  the  same  dimensions  were  turned 
from  iron  E. 

No.  1,  having  diameter  .565",  length  2.27". 

No.  2,  having  diameter  .565",  length  2.25". 

No.  1  was  broken  by  steady  tension,  and  at  tensile  limit  its 
diameter  was  .498",  length  2.80".  No.  2  was  broken  by  a  series 
of  jerks,  and  its  ruptured  dimensions  were,  diameter  .496", 
length  2.87" ;  the  ruptured  dimensions  of  No.  1  being,  diameter 
.407",  length  3.00". 

Comparison  of  Elevation  of  Limit  of  Stress,  upon  Irons  of  differ- 
ing Characteristics. 

The  first  series  of  experiments  (Nos.  1  to  12)  gave  indica- 
tions that  the  operation  of  the  law  was  less  felt  by  coarse  and 
brittle  irons,  and  l^y  those  of  a  steely  structure,  than  by  those 
of  a  more  fibrous  ductile  texture.  This  was  considered  to  be 
a  point  worthy  of  careful  examination,  and  a  series  of  com- 
parative experiments  was  made  upon  test-pieces  composed  of 
the  three  varieties  of  iron.  Thirteen  pieces  were  prepared, 


ELEVATION  OF   THE  LIMIT   OF   STKESS. 


45 


five  of  which  were  of  soft  charcoal  bloom  boiler-iron,  five  of 
coarse  contract  chain-iron,  and  three  of  a  fine-grained  bar  of 
iron  K,  a  very  pure  iron  with  high  tenacity.  These  pieces 
were  all  made  of  uniform  proportions,  and  were  tested  to  ten- 
sile limit  upon  the  same  day.  They  were  then  allowed  to  rest 
eighteen  hours,  and  again,,  tested.  Some  were  broken  at  this 
second  test ;  others  released  from  stress  at  tensile  limit,  and  fur- 
ther tested  after  varying  periods  of  rest,  as  per  following  table, 
in  which  Nos.  62  to  66  were  of  the  boiler-iron,  67  to  71  of  the 
contract  chain,  and  72  to  74  of  iron  K. 


Effect  of  Uniform  Rest  upon  Irons  of  widely  'different  Character. 

TEST-PIECES  RESTED  EIGHTEEN  HOURS. 


ULTIMATE  STRENGTH  GAIN  IN  STRENGTH 

PER  SQUARE  INCH. 

PER  SQUARE  INCH. 

NUMBER  AND  MARKS. 

REMARKS. 

First 
Strain. 

Second 
Strain. 

Pounds. 

Per  Cent. 

Pounds. 

Pounds. 

62,  Boiler  iron  . 

48,600 

56,500 

7,900 

16.0 

Not  broken. 

63, 

49,800 

57,000 

7,200 

16.4 

Broken.] 

64,           " 

49,800 

58,000 

9,200 

18.4 

Broken,  i      Average 

65,            " 

48,100 

54,400 

6,300 

13.1 

Broken,  f  15.8  per  cent. 

66,            " 

48,150 

55,550 

7,400 

15.0 

Broken.  J 

67,  Contract  chain  iron 

50,200 

54,000 

3,800 

7.5 

Broken.         ] 

68,        ' 

50,250 

53,200 

2,950 

5.8 

Not  broken. 

69,        «                  « 

50,700 

55,300 

4,600 

9.0 

Not  broken.  >  fi  Average 

70, 

49,600 

52,900 

3,300 

6.6 

Not  broken.  1         ^er  cent* 

71,       «                 « 

51,200 

52,800 

1,600 

3.2 

Not  broken.  J 

72  Iron  K    

58,800 
59,000 

64,500 
65,800 

5,700 
6,800 

9.6 
11.5 

Broken:l     Average 

73           ' 

74,          «       

56,400 

60,600 

4,200 

7.3 

Broken./  9'4Percent- 

These  experiments  confirmed  the  opinion  already  formed, 
and  indicate  that  a  bridge,  cable,  or  other  structure  composed 
of  iron  of  either  of  the  latter  two  varieties,  will  receive  com- 
paratively slight  benefit  from  the  operation  of  this  law ;  while 
ductile,  fibrous  metal,  which  possesses  greater  inherent  power 
to  resist  sudden  strains  than  does  the  iron  of  a  coarser  nature, 
although  the  latter  may  be  better  able  to  resist  steady  stress, 
gains  in  this  latter  power  to  a  greater  extent  by  the  effect  of 
strains  already  withstood. 


46  WROUGHT-IKON  AXD   CHAIN-CABLES. 


Supplemental  Tests  of  Nos.  62,  68,  69,  70,  and  71,  of  foregoing 

Test-Pieces. 

No.  62,  after  having  been  strained  to  the  tensile  limit  the 
second  time,  was  released  from  stress,  and  re-tested  after  one 
years  rest,  when  its  ultimate  strength  was  found  to  be  59,500 
pounds,  a  total  gain  of  22  per  cent  upon  the  original  strength. 

No.  68  was  rested  for  7  hours,  '41  hours,  and  24  hours, 
and  after  each  rest  repulled  to  the  tensile  limit,  with  results  as 
follows  (the  first  two  tests  being  included  for  ready  compar- 
ison) :  Strength,  first  strain,  50,250  pounds ;  rested  18  hours, 
strength  53,200  pounds ;  rested  7  hours,  strength  54,700  pounds  ; 
rested  41  hours,  strength  54,500  pounds;  rested  24  hours, 
strength  54,000  pounds. 

No.  69.  First  strain,  strength  50,700  pounds ;  rested  18  hours, 
strength  55,300  pounds;  rested  7  hours,  strength  53,150 
pounds ;  rested  41  hours,  strength  56,600  pounds ;  rested  24 
hours,  strength  54,000  pounds. 

No.  70.  First  strain,  strength  49,600  pounds;  rested  18 
hours,  strength  52,900  pounds;  rested  8  hours,  strength  51,000 
pounds;  rested  16  hours,  strength  54,800  pounds;  rested  24 
hours,  strength  53,000  pounds. 

No.  71.  First  strain,  strength  51,200  pounds ;  rested  18  hours, 
strength  52,800  pounds ;  rested  8  hours,  strength  54,900  pounds ; 
rested  16  hours,  strength  52,750  pounds;  rested  24  hours, 
strength  51,750  pounds. 

The  four  pieces  were  broken  at  the  strains  last  given. 

Experiments  with  Two  Sets  of  Test-Pieces :    One  Set  cut  from 

JBars  in  their  Normal   Condition,  the  other  from  the  same  Bars 

after  the  Latter  had  been  pulled  asunder  by  Tension. 

Nineteen  bars  of  various  irons  were  selected,  and  from  each 

a  cylindrical  test-piece  was  prepared :  the  bars  were  then  fitted 

with  heads,  and   pulled  asunder  by  tension.     Another  set  of 

cylinders  was  prepared  by  cutting  the  necessary  length  from 

one  of  the  broken  ends,  about  six  inches  from  the  point  of  rup- 


ELEVATION  OF   THE  LIMIT   OF   STRESS. 


47 


ture.  Both  sets  of  cylinders  were  tested,  with  results  as  per 
following  table,  showing  a  great  gain  in  strength  in  all  cases 
when  the  material  could  be  classed  as  wrought-iron,  but  none 
when  it  was  steel.  Hence  we  infer  that  excess  of  carbon  de- 
prives iron  of  the  power  to  gain  strength  through  the  action  of 
this  law. 

Experiments  Nos.  75  to  96.  —  Comparison  of  Strength  of  Two  Sets  of  Test- 
Pieces,  the  first  of  which  was  cut  from  Bars  in  their  Normal  Condition,  and 
the  second  from  the  same  Bars  after  the  latter  had  been  pulled  in  Two. 


NO.   OF 

TEST. 

SIZE  OP 
BAB. 

NAME  OF 
IRON. 

STRESS  REQUIRED  TO  BREAK 
THE    TEST  -  PIECES    PER 
SQUARE  INCH. 

STRENGTH  OF  SECOND  SET 
OVER  FIRST. 

First  Set. 

Second  Set. 

Pounds. 

Per  Cent. 

Inch. 

Pounds. 

Pounds. 

Per  Sq.  Inch. 

75 

if 

K 

53,520 

72,700 

19,180 

35.8 

76 

•  Hi 

K 

53,920 

71,800 

17,880 

33.1 

77 

113 

C 

47,875 

63,560 

15,685 

32.7 

78 

l|6 

C 

48,600 

65,000 

16,400 

33.7 

79 

If 

C 

56,000 

73,000 

17,000 

30.3 

80 

li 

C 

52,000 

67,900 

15,900 

30.6 

81 

1 

7_ 

C 

45,800 

63,300 

17,500 

36 

82 

1 

| 

B 

51,900 

72,000 

20,100 

38.7 

83 

.    1 

1 

B 

53,600 

68,700 

15,100 

28.1 

84 

1- 

. 

J 

50,350 

68,400 

18,050 

35.8 

85 

1 

J 

50,400 

67,700 

17,300 

34.3 

86 

F 

50,180 

66,400 

16,220 

32.3 

87 

F 

50,400 

67,200 

16,800 

33.3 

88 

E 

50,080 

68,000 

17,920 

35.7 

89 

E 

50,100 

70,100 

20,000 

39.9 

90 

: 

| 

L 

58,390 

69,200 

10,810 

18.5 

91 

;  , 

6 

L 

59,290 

67,160 

7,870 

13.2 

92 

•  •• 

L 

75,233 

76,600 

.... 

Q3 

1 

L 

84,800 

i/O 

94 

1 

L 

74,600 

72,600 

Decrease. 

95 

I7 

V 

L 

66,500 

96 

ig 

L 

66,800 

73,900 

5,250 

*7.9 

The  test-pieces  from  Nos.  75  to  89  inclusive  were  made  from 
ordinary  commercial  bar-iron  of  various  degrees  of  ductility. 
All  show  a  remarkably  great  strength,  caused  by  tension  upon 
the  entire  bars. 


48 


"\VEOUGHT-IRON  AND   CHAIN-CABLES. 


The  interval  of  time  between  the  two  sets  of  tests  was  not 
noted,  but  it  was  several  days. 

There  is  no  marked  difference  in  the  amount  of  elevation, 
except  upon  the  test-pieces  made  from  L,  which  was  a  weld- 
steel,  although*  sent  to  us  as  chain-iron.  With  this  metal  the 
results  were  exceedingly  irregular,  and  it  was  thought  advisable 
to  make  a  few  careful  tests  upon  it.  Four  pieces  were  there- 
fore prepared  from  a  bar  of  |"  diameter,  which  were  tested  to 
the  tensile  limit,  and  then  rested  for  one  hour,  one  day,  one 
week,  and  one  month,  respectively,  when  they  were  re-tested 
with  results  as  follows :  — 

Experiments  Nos.  97  to  100.     Material  "Iron"  L  (Weld  Steel). 


ORIGINAL 

STRENGTH  PER 

GAIN  IN 

8 

DIMENSIONS. 

SQUARE  INCH. 

STRENGTH. 

;r 

PERIOD  or  REST. 

t> 
& 

Diameter. 

Length. 

At  first 
Test. 

At  second 
Test. 

Pounds. 

Per  Cent. 

Inches. 

Pounds. 

Pounds. 

97 

.500 

2.25 

59,078 

58.619 

1  hour    .... 

—459 

... 

98 

.500 

2.25 

58,569 

57,805 

Iday      .... 

-764 

..  . 

99 

.496 

2.25 

59,000 

59,653 

1  week  .... 

+  653 

1. 

100 

.501 

2.25 

59,859 

61,694 

1  month      .     .     . 

+  1,834 

3. 

The  entire  series  of  tests  by  tension  upon  this  metal  indicates 
such  irregularity  in  its  strength  that  the  foregoing  tests  do  not 
possess  a  positive  value ;  but  they  indicate  that  there  is  a  great 
difference  between  the  action  of  weld-steel  and  even  steely 
irons,  and  still  greater  between  it  and  fibrous  iron  when  ex- 
amined in  reference  to  the  action  of  this  law.  We  obtain  no 
positive  evidence  that  any  increase  of  strength  is  caused  in 
steel,  by  rest  after  strain. 


THE  CABLE.  49 


SECTION   V. 

THE   CABLE. 

THE  information  which  we  have  gained  by  the  results  of  our 
tests  of  round  bars  has  its  value  in  determining  the  char- 
acteristics of  a  suitable  cable-iron,  but  it  does  not  supply  us 
with  all  that  we  need. 

The  cable -link  consists  of  a  round  bolt,  twelve  diameters  in 
length,  which  has  been  bent  into  an  oval  form,  and  the  ends 
welded  together.  A  stud  or  stay  is  introduced  between  the 
sides,  to  prevent  closure  under  stress,  and  kinking,  while  the 
cable  is  being  handled  or  used. 

The  tension  tests  upon  the  bars  show  us  what  strength 
should  exist  in  each  of  the  sides  of  the  link ;  and  the  impact 
tests  give  us  an  idea  as  to  the  power  of  the  transverse  sections 
of  the  ends  to  resist  stress  suddenly  applied,  if  the  process  by 
which  the  bar  is  transformed  to  a  link  has  no  power  to  change 
the  qualities  as  found  in  the  bars. 

This  process  involves  twice  reheating  and  hammering  the 
ends  of  the  bolts,  —  once  to  make  the  scarfs,  and  once  to  make 
the  welds,  while  the  butt  end  of  the  link  has  at  the  same  time 
with  the  ends  been  heated  once  for  bending.  This  forging  and 
re-heating  has  a  tendency  to  lower  the  elastic  limit  and  strength 
of  the  two  ends  of  the  bolt  upon  which  the  weld  is  made ;  the 
process  of  bending  affects  some  irons  injuriously;  and  the  com- 
paratively incompressible  stud,  which  prevents  closure,  alters 
the  nature  of  the  strains. 

If  none  of  these  causes  reduced  the  strength  of  a  link,  and 


50 


WEOUGHT-IRON   AND   CHAIN-CABLES. 


the  single  area  of  each  end  should  be  so  strengthened  by  its 
arched  form  that  it  would  be  equal  to  the  two  sides  combined, 
the  strength  would  be  just  twice  that  of  the  bar  from  which  it 
was  made. 

A  suitable  chain-iron  is  one  which  will  develop  in  the  link 
form  the  greatest  and  most  uniform  proportion  of  this  two 
hundred  per  cent.  And  the  development  of  a  low  or  irregular 
proportion  indicates  that  the  iron  is  not  suitable.  The  diver- 
gence from  the  two  hundred  per  cent  marks  the  extent  to 
which  an  iron  can  be  called  suitable. 

The  causes  which  operate  upon  all  irons  to  reduce  their  per- 
centage are,  first,  the  weld ;  second,  the  stud.  We  have  tested 
a  large  number  of  chain-links  to  destruction,  and  their  action 
under  the  strain  of  tension  has  been  carefully  noted.  We  find 
that  the  lowest  percentages  of  the  bar's  strength  are  developed 
by  those  irons  which  do  not  permit  strong  and  thorough  weld- 
ing by  ordinary  processes ;  and  that,  in  breaking  links  of  all 
variety  of  irons,  the  weld  end  is  generally  the  weak  part  of  the 
link ;  and  that  with  certain  types  of  iron  this  weakness  is  so 
great  and  of  so  frequent  occurrence  that  cables  made  from  such 
iron  are  very  unreliable. 

In  the  rupture  of  435  links,  333  of 
them  broke  at  the  weld  end,  86  at  the 
butt  end,  and  16  on  the  side. 

The  most  ordinary  location,  of  the 
rupture,  if  we  except  irons  Fx,  F,  L, 
M,  and  Px,  was  at  the  quarter  of  the 
weld ;  which  rupture  is  produced  by  a 
resolution  of  the  force  of  direct  ten- 
sion and  the  resistance  opposed  by  the 
stud. 

The  sketch  will  show  the  parts  of  the 
links  designated  as  quarter  weld,  &c. 

An  examination  of  the  records  of 
the  strength  of  links,  and  of  the  percentage  of  the  bar's 
strength  developed  by  the  links,  will  show  that  all  of  those 


THE  CABLE.  51 

links  which  broke  "through  the  weld"  were  very  weak  and 
irregular  in  both  factors.  Hence  an  iron  whose  weld  is 
through  any  cause  unreliable  is  not  suitable  for  cable. 

Experiments  indicate  that  we  cannot  strengthen  the  link  by 
changing  the  location  of  the  weld,  and  our  only  resource  is  to 
select  such  iron  as  is  least  injured  by  the  process  of  welding. 

Among  the  causes  which  produce  deficiency  in  welding 
properties,  there  are  two  which  produce  great  tenacity  in  the 
bar,  viz.,  chemical  peculiarities  and  excessive  work:  therefore, 
when  excessive  tensile  strength  is  found  to  exist  in  a  bar  as 
tested  by  tension,  it  should  be  regarded  as  a  probable  indication 
of  deficient  welding  properties.  As  may  be  seen  by  the  records 
of  tension  and  impact  compared,  high  tenacity  in  the  bar  fre- 
quently indicates  a  lack  of  power  to  resist  sudden  strains. 
Therefore,  in  judging  iron  by  tensile  strength  alone,  it  should 
be  considered  as  more  than  probable  that  the  strongest  bars  will 
produce  the  weakest  cables,  although  there  will  undoubtedly  be 
in  each  of  such  a  few  links  with  greater  strength  than  can  be 
developed  by  irons  of  less  tenacity. 

The  second  cause  which  tends  to  prevent  the  link  from 
developing  twice  the  strength  of  the  bar  is  the  stud. 

Our  experiments  lead  us  to  consider  that  the  opinion  which 
is  generally  entertained,  and  which  is  backed  by  the  most  emi- 
nent authorities,  that  the  studded  link  is  stronger  than  the 
unstudded  one  made  from  the  same  iron,  is  erroneous,  both  in 
principle  and  in  fact. 

Rankine,  in  his  "Manual  of  Machinery"  says,  "An  unstud- 
ded chain  has  about  two-thirds  of  the  strength  of  a  studded 
chain  of  the  same  diameter  of  wire."  John  Anderson,  LL.D., 
superintendent  of  machinery  to  the  War  Department,  Wool- 
wich, in  a  work  published  in  1872,  says,  "It  is  to  be  noted, 
whatever  the  explanation  may  be,  that  the  stayed-link  chain, 
when  made  of  the  same  diameter  of  iron  as  the  open-link,  is 
stronger  than,  the  other  in  the  proportion  of  9  to  6.  The  office 
of  the  stud  is  to  prevent  the  collapse  of  the  link,  and  thereby 
intercept  the  shearing  action  due  to  the  wedge  action  of  one 
link  within  the  other." 


52  WROUGHT-IRON   AND   CHAIN-CABLES. 

American  authorities  coincide  with  the  above  opinions,  with 
which,  however,  we  entirely  differ.  Theoretically  it  should  not 
be  stronger,  actually  it  is  weaker,  than  the  open-link. 

Theory  indicates  that  when  the  links  are  without  studs  they 
might  stretch  until  they  nipped  each  other,  and  then  be  in  the 
best  possible  position  to  resist  stress ;  the  sides  being  parallel  and 
separated  but  by  their  own  diameter,  the  ends  so  closed  together 
that  the  stress  is  received  and  transmitted  through  bearing  sur- 
faces much  greater  than  before  the  parts  had  yielded  to  stress. 

Our  experience  in  testing  cable  links  showed  us  that  with  all 
classes  of  iron  this  tendency  to  assume  the  strongest  possible 
form  existed,  but  in  very  different  degrees ;  and  in  this  differ- 
ence we  find  a  possible  reason  for  the  different  conclusions  that 
have  been  arrived  at  by  the  English  experimenters  and  by  our- 
selves. The  English  use  for  chain-cables  iron  of  great  tenacity, 
and  the  studs  to  their  links  are  made  of  malleable  iron. 

Our  experiments  have  been  made  both  with  links  of  iron  of 
similar  character,  and  with  others  made  from  iron  with  medium 
and  low  tenacity,  but  with  great  ductility  and  power  of  flexure. 
In  all  cases  we  have,  however,  used  the  ordinary  cast-iron  stud. 

Experiments  made  upon  iron  of  a  soft  ductile  type  showed 
that  the  excess  of  the  strength  of  the  unstudded  link  over  that 
of  the  studded  ranged  from  twelve  to  seventeen  per  cent, 
averaging  about  fifteen  per  cent,  of  the  strength  of  the  studded 
links ;  while  with  links  made  of  iron  of  a  coarse,  hard  type  the 
excess  of  strength  was  about  five  per  cent,  as  shown  by  the 
following  tests. 

EXPERIMENTS  UPON  COMPARATIVE  STRENGTH  OF  STUDDED 

AND  UNSTUDDED  LlNKS  MADE  FROM  SOFT  DUCTILE  IRONS 

(C  AND  F) ;  DIAMETER  OF  IRON,  1J". 

The  links  were  arranged  in  seven  sections,  of  three  links 
each ;  of  which  the  centre  link  was  in  each  case  an  open  one, 
and  the  two  end  links  (E  L)  were  connected  to  the  proving-bar 
by  means  of  links  of  considerably  greater  diameter  (lT7g"). 

After  pulling  each  section  until  one  of  the  links  broke,  the 


THE   CABLE. 


53 


pair  remaining  was  again  pulled  till  one  broke,  and  finally  the 
unbroken  remaining  link  was  broken. 

The  results  of  the  tests  were  as  follows :  — 


Test 
No. 

Number 
and  Arrangement  of 
Links. 

Link 
which 
Broke,.. 

Stress 
at 
Rupture. 

Test 
No. 

Number 
and  Arrangement  of 
Links. 

Link 
which 
Broke. 

Stress 
at 
Rupture. 

Pounds. 

Pounds. 

1 

1 

3 

2 

Stud,  Open,  Stud, 
0.  S. 

S. 

S. 

87,360 
89,088 

4 
4 

1 
1 

0. 
0. 

E.  L.        96,000 
O.         104,000 

1 

1 

O. 

E.  L. 

86,400 

5 

3 

S.  0.  S. 

8. 

90,624 

1 

1 

0. 

E.  L. 

74,880 

5 

1 

O. 

O. 

105,576 

2 

3 

S.  O.  S. 

8. 

91,584 

6 

3 

S.  O.  S. 

S. 

82,176 

2 

2 

O.  O. 

O. 

99,844 

6 

2 

O.  S. 

S. 

91,776 

2 

1 

0. 

E.  L. 

77,280 

6 

1 

O. 

O. 

100,128 

2 

1 

O. 

0. 

82,170 

7 

3 

S.  O.  8. 

S. 

79,488 

3 

3 

S.  O.  S. 

S. 

96,960 

7 

2 

O.  O. 

O. 

105,600 

3 

2 

O.  O. 

E.  L. 

92,544 

7 

1 

O. 

E.  L. 

67,200 

3 

2 

0.0. 

0. 

104,064 

7 

1 

0. 

E.  L. 

89,280 

4 

3 

S.  O.  S. 

Pin 

85,632 

7 

1 

0. 

Pin 

82,176 

4 

3 

S.  0.  S. 

S. 

98,688 

7 

1 

O. 

O. 

109,632 

The  bar  from  which  sections  Nos.  1  and  2  were  made  had  a 
tensile  strength  of  59,000  pounds ;  Nos.  3  and  4  were  from  bars 
with  57,000  pounds ;  Nos.  5  and  6  from  bars  with  54,000  pounds ; 
and  No.  7  from  a  bar  with  57,700  pounds  tensile  strength. 

In  every  case  in  which  there  were  both  open  and  studded 
links  connected,  the  studded  link  first  broke.  In  six  tests,  the 
open  link  of  1J"  diameter,  of  good  iron,  broke  the  If'g"  ^n^  °^ 
inferior  iron,  and  twice  the  shackle-pin  of  steel. 

The  maximum  strength  of  the  studded  links  on  the  first  pull 
was  96,960  pounds ;  the  minimum,  79,488  pounds ;  the  average 
of  six,  88,030  pounds. 

In  three  cases  where  a  studded  link  was  pulled  the  second 
time,  the  maximum  strength  was  98,688  pounds  ;  the  minimum, 
89,088  pounds ;  and  the  average,  93,188  pounds. 

The  maximum  strength  found  in  an  open  link  was  109,632 
pounds,  on  a  sixth  pull;  the  next  was  105,576  pounds  on  a 
second  pull ;  and  the  minimum,  upon  any  pull,  was  82,170 
pounds  —  the  average  strength  of  eight  being  101,327  pounds; 
the  inferior  iron  (contract  chain-iron),  of  which  the  end  links 
were  made,  breaking  upon  second  and  third  pulls,  at  from 
67,200  pounds  to  96,000  pounds,  averaging  82,383  pounds. 


54  WROUGHT-IKON  AND  CHAIN-CABLES. 

From  which  we  deduce,  that,  of  the  same  iron,  an  unstudded 
cable  would  have  exceeded  in  strength  the  studded  one,  in 
actual  strength,  over  13,000  pounds,  or  15  per  cent ;  and  that 
after  having  been  subjected  to  stress  sufficient  to  break  the 
studded  links,  the  unstudded  cable  would  have  still  proved 
reliable  ;  and,  further,  that  a  vessel  provided  with  a  studded 
cable  made  of  this  good  chain-iron  of  1J"  diameter,  of  which 
150  fathoms  would  weigh  five  tons,  would  have  possessed  more 
reliable  ground-tackle  than  if  the  cable  had  been  of  the  l-j%" 
contract-iron,  weighing  eight  tons. 

During  the  experiment  recorded,  several  times  it  happened, 
that,  either  through  the  stress  or  the  recoil,  one  of  the  studded 
links  became  an  open  one,  by  the  stud  splitting  and  flying  out. 

In  addition  to  the  evidence  given,  abstracts  from  our  tests 
show  that  in  breaking  thirty-three  sections  of  links  of  iron 
Fx,  D,  O,  and  N,  which  were  composed  of  both  studded  and 
unstudded  links,  in  twenty-nine  cases  the  link  which  broke  was 
a  studded  one. 

From  the  facts  recorded,  we  feel  that  we  are  justified  in 
saying,  that  beyond  doubt,  when  made  of  American  bar-iron, 
with  cast-iron  studs,  the  studded  link  is  inferior  to  the  un- 
studded one  in  strength. 

Therefore  we  place  the  stud  as  next  to  the  weld  among  the 
elements  which  tend  to  prevent  the  individual  links  from  de- 
veloping the  utmost  possible  strength. 

DESCRIPTION  OF  METHOD  OF  TESTING  CABLES. 

Our  records  embrace  the  results  of  strength,  &c.,  obtained 
by  the  rupture  of  229  sections  of  cables,  of  various  diameters 
and  lengths,  made  from  eighteen  different  irons. 

These  are  given  in  the  tabulated  record  of  breaking  strains, 
arranged  in  the  order  of  the  relative  strength. 

The  history  of  the  test,  as  cable,  of  one  of  the  irons  (Fx),  is 
given  in  detail  below. 

The  links  were  generally  arranged  as  shown  in  the  cuts ;  the 
end  links,  Nos.  1  and  5,  and  centre  link,  No.  3,  being  unstud- 


THE  CABLE. 


55 


ded,  the  others  studded.  The  end  links  were,  in  some  cases, 
of  greater  diameter  than  the  links  to  be  tested,  in  which  case 
they  were  not  recorded  in  the  number  of  links  in  section. 


After  we  had  decided  upon  the  superior  strength  of  the 
unstudded  link,  our  test-sections  were  prepared  with  end  links 
of  the  same  size  and  iron  as  the  other  links,  but  without  studs. 

The  shackle-pins  were  oval,  and  made  to  correspond  with  the 
diameter  of  the  links. 


Test  as  Cable  of  Iron  Ex.     Links  arranged  as  per  Sketch.     Elongation  re- 
corded when  .03"  was  observed  on  No.  2  Link. 


H 

BL 

s  . 

3  . 

ELONGATION  OF 

I 

II 

h 

ELONGATION  OF  UN- 
BROKEN LINKS. 

P3    . 

R  g 

H  w 

SI 

g| 

H  0 

«« 

pa  - 

PQ  g 

02   5 

rf 

CO 

+ 

g| 

K 

I 

<N 

CO 

4 

3 

^ 

Us 

6 

0 

6 

|H 

c'  a 

o  -5 

(^ 

^p 

<j 

q 

" 

B 

& 

* 

B 

fa  > 

^5 

fa 

^ 

cc 

00 

„ 

Pounds. 

„ 

„ 

n 

Pounds. 

n 

„ 

„ 

1 

3 

34,800 

.03 

.11 

.03 

70,300 

4 

Q.W. 

.50 

.62 

.  . 

H 

3 

44,400 

.03 

.16  !  .03 

81,400 

2 

T.  W. 

.  . 

.70 

.72 

3 

61,100 

.03 

.14    .05 

111,000 

2 

Q.B. 

.  . 

1.00 

.70 

ij 

3 

78,000 

.05 

.24 

.03 

124,000 

3 

W. 

1.45 

.   . 

.75 

ji 

3 

80,000 

03 

.28 

.04 

153,000 

2 

Q.W 

.  . 

1.15 

1.00 

if 

3 

98,000 

.03 

.28 

.06 

168,000 

2 

Q.W 

.  . 

1.85 

1.25 

i| 

3 

100,000 

.03 

.26 

.04 

185,000 

2 

Q.W. 

.  . 

1.20 

1.40 

11 

3 

110,000 

.03 

.22 

.03 

205,600 

3 

T.  W. 

1.60 

.  . 

1.30 

2 

3 

117,200 

.03 

'.19 

.04 

240,000* 

1.50 

1.70 

1.60 

These  tests  indicate,  that  with  ordinary  chain-iron,  although 
the  first  stretch  of  the  open  link  is  produced  by  a  much  lower 
stress  than  that  which  the  studded  one  withstands,  yet,  upon 

*  Not  broken. 

Five  ruptures  occurred  on  link  No.  2,  one  on  No.  4  studded,  and  two  on  open  links,  in  one 
of  which  the  weld  drew.  The  elongation  produced  upon  the  open  links  by  the  stress  which 
broke  the  studded  ones  was  not  sufficient  to  greatly  impair  their  usefulness :  the  1",  with 
original  inner  diameter  of  1.55",  being  reduced  to  1.40";  the  1J",  original  inner  diameter  2.8", 
after  stress,  2.50";  and  the  others  in  proportion,  there  being  sufficient  room  for  the  links  to 
traverse  freely. 


56 


^VROUGHT-IRON   AND   CHAIN-CABLES. 


the  strain  becoming  more  severe,  the  disproportion  in  its  effects 
becomes  less,  and  that  frequently  the  open  link  is  still  service- 
able after  the  studded  link  has  broken. 

The  following  abstract  shows  the  extreme  variation  that  we 
have  found  in  the  strength  of  cable  of  the  same  size,  made  from 
several  irons.  We  gather  from  it  that  a  variation  of  from 
five  to  seventeen  per  cent  may  be  expected  in  the  strength  of 
ordinary  cables ;  and  that,  if  proper  care  is  not  exercised  in 
selecting  the  material,  the  average  variation  may  rise  from 
twelve  to  twenty-five  per  cent  of  the  strength  of  the 

strongest. 

Variation  in  Strength  of  Cables. 


i 

an 

is 

"-1  E- 

STRENGTH  or  CABLE. 

VARIATION  ix 
STRENGTH. 

0  » 

•>§ 

VARIATION  IN 
STRENGTH  BY  INCLITD- 

1NG  OMITTED  LlNKS. 

-^ 

W  J3 

•    &< 

o 

tf  a 

jj 

3 

§ 

3 

4 

*a     S 

Is 

c 

*j 

M  S 

S 

.§ 

B 

Sv-.S 

ui  a 

1 

B 

M 

|S 

| 

fl 

£°3 

II 

Pounds. 

Pounds. 

1 

6 

79,200 

67,600 

11,600 

14. 

P. 

18,800 

23.7 

11 

7 

89,280 

80.900 

8,380 

9.4 

P. 

13,200 

14.7 

11 

7 

122,100 

101,700 

20,400 

16.6 

K.  i\r.  o. 

31,100 

25 

1   5_ 

1 

115,000 

109,000 

6,000 

5 

M. 

40,000 

34.7 

If 

9 

137,200 

125,000 

12,200 

8 

M.  Fx. 

42,200 

30.7 

If! 

2 

155,040 

139,400 

15,640 

10 

, 

. 

.  . 

i 

9 
12 

173,000 
199,000 

147,000 
168,000 

26,000 
31,000 

15 
15.5 

M.  K.  P. 
M. 

38,400 
74,000 

22.2 
37" 

2 

214,160 

194,880 

19,280 

9 

, 

. 

.  . 

1|.6 

8 

231,300 

191,000 

40,300 

17 

Fx. 

45,800 

19.7 

Mi 

2 

231,940 

204,400 

27,540 

12 

, 

, 

.  . 

4 

6 

252,960 

215,000 

37,960 

11 

Fx. 

47,360 

18.6 

0 

8 

283,200 

240,000 

43,200 

15 

•      • 

•      • 

•  • 

Aver 

age 

•      - 

•      • 

•      • 

12.1 

.  .    . 

-      • 

25.1 

The  excessive  variation  in  case  of  the  If"  is  due  to  the  fact 
that  a  portion  of  a  lot  of  excellent  chain-iron,  C,  was  composed 
of  very  inferior  material,  which  was  very  irregular  in  strength ; 
the  strongest  link  in  the  lot  breaking  at  231,300  pounds,  and 
five  out  of  eleven  sections  breaking  at  less  than  200,000  pounds ; 
the  minimum  being  that  in  the  table,  191,000  pounds. 


THE  CABLE. 


57 


No  system  of  tests  made  upon  cable-bolts  alone  would  have 
detected  with  certainty  this  inferior  iron.  Had  the  iron  been 
furnished  in  thirty-feet  bars,  each  bar  would  have  produced 
sixteen  bolts,'  with  a  remainder  of  twenty-four  inches  for  test 
purposes,  the  test  of  which  would  have  given  valuable  evidence 
of  the  character  of  the  sixteen  links. 

WEIGHT  or  CHAIN-CABLES. 

The  chain-cables  manufactured  by  the  ordinary  systems  are 
very  heavy ;  and  we  are  led  by  the  results  of  our  investigation 
to  believe  that  their  weight  can  be  reduced  advantageously, 
and  as  great,  if  not  greater,  safety  be  secured. 

The  weight  and  dimensions  of  various  portions  of  cables  of 
different  sizes,  and  of  full  cables,  of  the  length  ordinarily  used, 
are  given  in  the  following  table :  — 

Number  and  Weight  of  Links  in  150  Fathoms  of  Cable. 


M 

Hi 

IP 

WEIGHT  or 
STUDS. 

FINISHED  LINKS. 

NUMBER  OF 
LINKS  IN 
FATHOM. 

TOTAL  WEIGHT  OP 
150  FATHOMS  CABLE. 

Length. 

Width. 

Weight. 

Studded 
Link. 

Open  Link. 

Pounds. 

j 

Pounds. 

Pounds. 

Pounds. 

1" 

2,925 

.25 

5*1"  1     3y*-" 

2.90 

194 

8,665 

7,934 

JA 

2.775 

.25 

6-i-       311 

3.43 

184 

9,701 

9,008 

4 

2,700 

.44 

n  4 

4 

4.22 

18 

11,650 

10,462 

IJL 

2,550 

.44 

GI  o 

4-2_ 

4.89 

17 

12,726 

11,604 

$ 

2,450 

.50 

716 

4J7g 

5.68 

16 

14,236 

13,020 

2,325 

.50 

7ft 

4ft 

6.50 

15J 

15,442 

14,279 

1-36 

2,250 

.62 

7ft 

41^ 

7.52 

15 

17,326 

15,931 

1T76 

2,100 

.62 

8 

5ft 

8.50 

14 

18,256 

16,954 

1 

2,025 
1,950 

.75 
.75 

tft 

^T96 

9.70 
10.87 

13 

20,143 
21,697 

18,624 
20,234 

56 

1,875 

.06 

9 

5    1 

12.45 

124 

23,996 

22,008 

'    11 

1,800 

.06 

9ft 

6 

13.81 

12 

25,510 

23,602 

•  I6 

1.725 

.25 

^156 

15.47 

11£ 

27,480 

25,330 

j.j 

1,650 

.25 

10ft 

6ft 

17.05 

11 

28.933 

26.870 

•j  • 

1,650 

.50 

61.2 

19.00 

11 

32,334 

29.859 

H 

1,575 

.50 

10i! 

6il 

20.80 

101 

33.744 

31.382 

2 

1,500 

2.09 

2332 

10 

36,125 

32,990 

1,500 

2.09 

lift 

7-6- 

25.38 

10 

39,215 

36,080 

01  ^ 

1,425 

2.25 

lift 

710 

27.72 

^i 

40,811 

37,605 

4 

1,350 

2.25 

1211 

7fl 

30.04 

9 

41,864 

38,827 

58  WROUGHT-IRON  AND  CHAIN-CABLES. 

METHODS  BY  WHICH  THE  WEIGHT  OF  CABLES  CAN  BE  RE- 
DUCED IN  A  GREATER  RATIO  THAN  THE  STRENGTH. 

Two  methods  of  reducing  the  weight  of  chain-cables,  without 
impairing  their  strength,  present  themselves  as  results  of  our 
experiments;  the  first  founded  upon  our  investigation  of  the 
action  of  the  rolls  and  our  impact  tests  combined,  and  the 
second  upon  comparative  experiments  of  the  strength  of  studded 
and  open  links. 

I.  We  have  found,  that,  when  made  from  the  same  material, 
the  large  bars  possess  less  strength,  in  proportion  to  their  areas, 
than  the  small  ones,  as  opposed  to  steady  strain,  and  generally 
much  less  absolute  power  to  resist  sudden  strains. 

The  strength  per  square  inch  of  a  li"-bar  being  54,000 
pounds,  that  of  the  2"  would  be  50,000  pounds,  and  the  entire 
strength  of  the  1J",  112,000  pounds;  which  is  71  per  cent  of 
that  of  the  2",  viz.,  157,000  pounds. 

If  the  two  bars,  2"  and  If",  were  equally  valuable  in  every 
respect  for  cable,  and  both  in  link  form  developed  the  same 
percentage  of  the  bar's  strength,  say  163  per  cent,  the  strength 
of  the  1§"  cable  would  be  182,600  pounds,  which  is  71  per  cent 
of  that  of  the  2",  viz.,  256,000  pounds ;  while  its  weight,  23,996 
pounds,  would  be  but  66.4  per  cent  of  that  of  the  2",  viz., 
36,125  pounds. 

If  it  be  considered  that  the  loss  in  actual  power  to  resist 
steady  tension  is  not  counterbalanced  by  the  gain  in  reduced 
weight,  the  comparative  powers  to  resist  sudden  strains  should 
be  considered.  It  is  more  than  probable  that  the  greater  work 
given  to  the  1J"  will  have  so  increased  its  ductility  that  its 
power  to  resist  sudden  strains  will  prove  greater  than  that  of 
the  2"  cable. 

These  views  are  borne  out  by  many  of  our  experiments,  from 
which  we  will  select  the  bars  of  iron  N  for  comparison.  This 
iron  was  sent  to  us  by  a  prominent  manufacturer,  in  answer  to 
an  order  for  "  samples  of  best  cable-iron." 

The  2"-bar  had  tenacity  51,748  pounds,  and,  when  broken  by 


THE   CABLE.  59 

tension,  had  a  very  slight  reduction  of  area  and  elongation : 
broken  by  impact,  it  proved  very  brittle,  and,  while  in  no  ways 
nicked  or  injured,  would  break  like  a  pipe-stem  by  moderate 
blows. 

Tested  as  cable,  the  links  developed  but  141  per  cent  of  the 
bar's  strength ;  viz.,  232,000  pounds. 

The  liT-bar,  with  tenacity  56,344  pounds,  when  tested  by 
tension,  reduced  in  area  to  60  per  cent  of  the  original,  and 
elongated  23  per  cent. 

Tested  by  impact,  it  proved  fairly  tough,  deflecting  to  over 
60°  before  breaking,  and,  when  circled  with  a  score,  resisted  to 
a  greater  extent  than  did  the  2"  in  its  normal  condition. 

Tested  as  cable,  the  links  developed  164  per  cent  of  the  bar's 
strength,  breaking  at  195,500  pounds,  or  at  84  per  cent  of  the 
strength  of  the  2". 

In  this  case,  there  can  be  no  doubt  but  that  the  smaller  and 
lighter  cable  would  have  proved  the  most  reliable. 

Irregularity  in  strength  is  a  great  fault  in  cable-iron :  this  is 
more  apt  to  occur  in  large  than  in  small  bars ;  one  reason  for 
which  is,  that  irregularity  in  heating  the  piles  produces  irregu- 
larity in  strength,  and  to  this  the  large  bars  are  more  greatly 
exposed  than  the  small  ones.  The  pile  and  resultant  bar  of  2" 
weighs  four  or  five  hundred  pounds,  and,  while  passing  through 
the  roll,  is,  of  course,  much  more  difficult  to  handle  than  a 
lighter  pile  or  bar :  there  are  greater  liabilities  of  "  buckling  " 
and  "  bending; "  and,  while  the  workmen  are  mauling  the  bar  to 
straighten  it,  the  next  bar  to  be  rolled  is  being  delayed  in  the 
furnace,  and  the  effects  of  variation  in  the  heat  are  not  pro- 
vided against  by  regulating  the  latter.  It  seems  but  natural, 
that,  if  the  pile  for  a  small  bar  is  heated  enough  for  rolling 
in  one  hour,  portions  of  the  large  pile  are,  in  the  same  time, 
equally  ready,  and  that  by  longer  delay  in  the  furnace  they 
become  overheated. 

The  effect  of  overheating  is  to  lower  both  the  elastic .  limit 
and  the  strength. 

Irregularity  in  the   workmanship  by  which   the   links   are 


60  WKOUGHT-IKON  AND  CHAIN-CABLES. 

manufactured  produces  irregular  strength  in  the  cable.  To 
this  the  larger  bars  are  exposed  to  a  greater  extent  than  the 
smaller  ones :  the  weld  is  less  apt  to  be  perfect.  A  small  bar 
is,  when  at  the  right  heat,  welded  by  a  few  quick  blows ;  and  the 
time  of  the  operation  is  not  great  enough  to  allow  the  iron  to 
become  cool.  With  a  large  bar  it  is  different.  It  requires  more 
and  harder  blows,  and  more  time  ;  and,  if  at  the  right  heat 
when  the  operation  is  begun,  it  may  be  too  cool  before  it  is 
ended,  or,  in  order  that  it  shall  not  be,  it  may  be  heated  a 
little  too  much  on  the  start ;  the  surface  of  the  weld  is  greater, 
and  is  more  exposed  to  the  danger  of  interposition  of  ashes, 
dust,  or  scoria,  either  of  which  will  prevent  a  perfect  weld. 

Finally,  if  the  cable  be  finished  without  any  accidental 
defect,  the  proof  of  the  2"  so  far  exceeds  that  of  the  If",  in 
proportion  to  its  strength,  that  it  is  possible  that  the  strength 
it  may  have  had  will  be  lowered  by  it. 

For  the  reasons  assigned,  we  are  of  the  opinion  that  the 
margin  of  safety  secured  by  the  use  of  a  cable  of  1§"  iron, 
weighing  twelve  tons,  is  equally  great  as  by  the  use  of  the  2", 
weighing  eighteen  tons. 

II.  The  second  method  of  reducing  the  weight  of  cables  con- 
sists in  the  substitution  of  open  for  studded  links. 

There  exists  a  strong  prejudice  against  the  use  of  cables 
made  from  links  without  studs.  This  prejudice  is  based  upon 
the  opinion  which  is  very  generally  entertained,  that,  first,  the 
open  link  is  not  as  strong  as  the  studded  one ;  second,  that, 
owing  to  the  want,  of  the  support  given  to  the  sides  by  the  stud 
when  used,  the  open  link  will  collapse  at  a  much  lower  strain 
than  the  studded  one  will,  and  that  this  collapse  will  be  so 
great  that  the  links  will  nip  each  other,  and  become  rigid  ;  and, 
third,  that  the  liability  of  the  relative  position  of  the  links  to 
become  misplaced  is  greater  with  the  open  than  with  the  stud- 
ded links,  from  which  cause  jams  may  occur  in  the  hawse-pipe 
when  the  cable  is  running  out,  or,  after  having  remained  some 
time  with  a  slack  cable,  a  sudden  squall,  tautening  it,  might 
produce  the  same  effect. 


THE  CABLE.  61 

• 

The  first  of  these  objections,  viz.,  that  the  open  link  is  weaker 
than  the  studded  one,  our  experiments  show  to  be  without  foun- 
dation. The  contrary  is  the  case  under  all  circumstances. 

We  are  led,  by  the  results  of  our  tests,  to  doubt  that  the 
second  objection  exists  to  the  extent  generally  supposed.  We 
find,  that,  in  all  cases,  the  open  links  begin  to  change  form 
at  a  lower  stress  than  the  studded  ones ;  but  the  sides  having 
straightened  somewhat,  the  stress  is  soon  resisted  by  the  tena- 
city of  the  material  itself,  and  unless  the  iron  is  very  soft 
and  ductile  (much  more  so  than  is  usually  the  case  with  chain- 
iron),  the  closure  does  not  continue  to  be  rapid ;  and  at  an 
extreme  stress,  sufficient  to  rupture  the  studded  link,  if  there 
be  one  in  the  section  under  test,  the  closure  has  not  been  so 
great  as  to  unfit  the  open  links  for  service. 

With  irons  F  and  O,  both  extremely  ductile,  some  of  the 
open  links  were  too  much  closed  for  service,  but  others  were 
not,  after  having  resisted  the  stress  which  broke  the  studded 
links.  Such  iron,  however,  will  not  often  be  made  into  cables ; 
and  we  have,  to  a  certain  extent,  a  resource  by  which  this  early 
closure  of  the  sides  may  be  delayed  with  all  irons.  • 

A  cable  made  of  bolts  of  £  of  an  inch  greater  diameter, 
without  studs,  will  possess  fully  twenty  per  cent  more  strength 
than  the  smaller  studded  cable,  and  will  weigh  but  a  trifle  more. 
For  instance,  the  total  weight  of  150  fathoms  or  ten  sections 
of  1 J"  studded  cable  would  be  20,143  pounds ;  and  that  of  150 
fathoms  or  ten  sections  of  1§"  open  cable  would  be  22,008 
pounds. 

Thus  the  difference  in  weight  would  be  but  1,865  pounds. 

The  probable  strength  of  the  1J';  studded  cable  would  be,  at 
greatest,  157,000  pounds ;  that  of  the  1 6",  if  studded,  182,000 
pounds,  and  if  unstudded  considerably  more ;  the  minimum 
difference  of  25,000  pounds  being  nearly  sixteen  per  cent  of 
the  entire  strength  of  the  li"  cable.  And,  as  the  action  of 
the  studs  tends  to  pry  open  such  welds  as  may  not  be  perfect, 
the  chances  for  regularity  in  strength  are  much  increased  by  its 
omission.  And  it  is  more  than  probable  that  the  extreme  stress 


62  WROUGHT-IRON   AND   CHAIN-CABLES. 

at  which  the  1J"  would  break  would  not  close  the  links  of  If" 
to  such  extent  as  to  render  them  unserviceable. 

The  third  objection  to  the  use  of  open-link  cables  is  that  it  is 
presumed  that  they  are  more  liable  to  become  fouled  and 
kinked  than  the  studded-link  cable,  while  being  stowed  in  the 
chain-locker,  or  when  slack,  and  the  vessel  changes  her  position 
without  tautening  the  cable. 

There  are  reasons  based  upon  facts  which  actually  exist, 
connected  with  the  process  of  manufacture,  which  justify  us 
in  the  assumption  that  the  danger  from  this  cause  is  not  so 
great  with  open-link  as  with  studded-link  cables.  [These 
reasons  are  given  at  length  in  the  original  report.] 

COMPARISON  OF  RESULTS  OBTAINED  BY  TENSION  UPON  SEC- 
TIONS OF  CABLE-LINKS,  AND  UPON  BARS  OF  THE  IRON 

FROM   WHICH   LINKS   WERE   MADE. 

It  was  considered  that  if  there  existed,  as  seemed  probable, 
a  relationship  between  the  strength  and  other  properties  of  the 
round  bar,  and  those  of  the  links  made  from  it,  it  would  be  a 
valuable  result  to  determine  such  relationship,  and  to  find  to 
how  great  an  extent  it  could  be  depended  upon,  and  within 
what  margins  it  existed ;  inasmuch  as  the  simple  and  inexpen- 
sive test  of  tension  upon  a  portion  of  a  bar  would  provide  data 
by  which  the  probable  strength  of  a  cable  made  from  it  could 
be  judged. 

The  following  tables  have  been  prepared  for  the  purpose  of 
developing  this  relationship,  and  finding  its  margins. 

We  find  that  with  iron  of  moderate  tenacity,  and  with  good 
welding  properties,  the  percentage  of  the  bar's  strength,  which 
is  carried  with  great  uniformity  into  the  link,  is  from  160  to 
175  per  cent ;  that,  with  irons  of  unsuitable  qualities,  this  per- 
centage is  frequently  low  and  frequently  high,  it  being  very 
irregular,  and  averages  of  less  than  155  per  cent,  made  up  of 
very  irregular  factors,  are  common ;  and  that  with  the  best 
chain-iron,  although  there  may  be  links  which  develop  over  175 
per  cent,  such  cases  are  rare. 


THE   CABLE. 


63 


Comparison  of  Strength  of  Cable-Links  and  Round  Bars. 
Iron  A. 


CABLE  LINKS. 

ROUND  BARS. 

RATIOS  OP 
LIN  KS&  BARS. 

•  of  Bar. 

sts  averaged. 

Stress  in  Pounds. 

1 

£  3 

f  Unbroken 

a 

£ 

C3 
O 

Stress  in  Pounds. 

ween  Stress- 
first  Stretch 
acture. 

tween 
nd  Links. 

i! 

i 

11 

M 

I 

"3 

111 

1 

if 

1 

!? 

~v 

£ 

2*1 

Is 

**  2**  a 

•=11  . 

S*s 

.   gg 

si 

cr1  Ml 

Wj 

0    A 

|j| 

o 

li 

|.2 

lll< 

'IS  3 

S3 

ll 

ij 

is 

£0 

•-§«§ 

•2  3 

•§3 

0 

£ 

^ 

fa 

cq 

24 

02 

«5 

fa 

fa 

£ 

2 

<A 

M 

1" 

3 

28,160 

71,328 

88,441 

39.5 

1.15" 

3 

28,127 

44,126 

54,690 

63.9 

61.9 

161.3 

2 

37,920 

89,040 

88,773 

42.5 

1.15 

3 

27,488 

53,997 

53,900 

51.2 

60.6 

164.9 

lj 

•> 

47,040 

114,680 

92,689 

41. 

1.2 

3 

33,888 

66,112 

53,879 

51.3 

57.7 

173.5 

2 

58,080 

134,400 

91,180 

43.2 

1.5 

3 

49,600 

78,944 

53,557 

62.8 

58.7 

170.3 

•2 

68,650 

153,600 

86,926 

44.7 

1.65 

2 

50,880 

91,680 

51,884 

55.4 

59.7 

167.5 

76,320 

174,260 

84,551 

43.7 

1.35 

2 

66,240 

111,984 

54,334 

59.1 

64.3 

155.6 

•2 

86,400 

214,560 

89,213 

40.3 

1.85 

2 

70,840 

123,840 

51,509 

57.2 

57.6 

173. 

1 

96,000 

252,960 

91,125 

38. 

2. 

2 

79,650 

141,120 

50,854 

56. 

56.7 

176. 

2 

11 

264,002 

84,023 



1.56 

9 

91,038 

157,588 

50,171 

57.8 

59. 

168.9 

Iron  B. 


IT7* 

13 

61,721 

149,790 

92,293 

41.1 

1.32 

4 

52,607 

84,862 

52,287 

61.8 

56.7 

176.4 

4 

87,937 

198,144 

86,637 

44.4 

1.23 

3 

74,113 

118,273 

52,895 

62.7 

59.9 

166.7 

1il 

4 

94,143 

221,650 

85,910 

41.5 

.... 

3 

87,743 

137,023 

53,109 

63. 

62.1 

161.7 

Iron  C. 


,       1 

48,600 

101,800 

102,414 

47.6 

2 

31,710 

57,125 

57,470 

55.5 

56.1 

178.2 

2 

61,450 

123,450 

98,573 

49.8 

.... 

1 

39,840 

71,040 

57,897 

56. 

57.5 

173.6 

2 

75,850 

133,400 

89,831 

56.8 

.... 

1 

46,080 

81,600 

54,949 

56.4 

61.1 

163.4 

7      i 

149,600 

92,175 

1 

53,000 

84,000 

51,756 

63.1 

56.1 

178. 

I1'    ' 

65,700 

157^900 

89,360 

44.4 



5 

61,440 

97,921 

55,404 

62.5 

61.2 

161.9 

1       7 

82,229 

180,500 

87,030 

45.5 

.... 

4 

68,880 

115,749 

55,879 

59.4 

64.4 

155.5 

[      13 

90,554 

199,830 

83,009 

45.5 

.... 

5 

75,420 

130,835 

54,410 

57.1 

65.9 

153. 

Iron  D.    First  Lot. 

2 

37,200 

96,200 

96,780 

38.6 

2 

29,300 

54,360 

54,687 

53.9 

56.6 

176.3 

2 
2 

53,800 
57,600 

123,800 
143,400 

100,896 
96,565 

43.1 
39.8 



1 

1 

34,560 
47,040 

68,160 
81,600 

55,550 
54,949 

50.7 
57.6 

55. 

56.8 

181. 
175.7 

2 

71,800 

178,300 

100,905 

40.3 

.  .  .  - 

1 

48,960 

92,160 

52,155 

53.1 

51.6 

193.4 

1 

85,000 

199,700 

96,287 

42.5 

.... 

1 

62,400 

111,360 

53,695 

56. 

55.7 

179.2 

1 

94,100 

231,400 

96,216 

41. 

.... 

1 

66,900 

126,720 

52,699 

52.8 

54.7 

182.6 

1 

94,600 

238,100 

86,236 

40. 

.... 

1 

76,800 

142,080 

51,459 

54. 

59.6 

167.6 

1 

134,400 

276,500 

88,000 

48.5 

.... 

1 

89,760 

160,700 

51,146 

55.8 

58.1 

172. 

Iron  D.     Second  Lot. 

1     36.200 

79,200 

100,843 

45.7 

1.25 

1 

26,300 

48,000 

61,115 

54.8 

60.6 

165. 

1 

45,000 

87,500 

88,814 

51.4 

1.55 

1 

33,100 

58,700 

59,582 

56.4 

67. 

149. 

1 

55,200 

113,000 

90,617 

48.8 

1.60 

1 

39,900 

72,300 

57,979 

55.2 

64. 

156.3 

1 

71,500 

137,200 

91,711 

52.1 

2.25 

1 

47,500 

86,800 

58,021 

54.7 

63.2 

158. 

1 

80,100 

173,000 

97,906 

46.3 

2.50 

1 

58.200 

101.200 

56,505 

57.5 

58.5 

170.8 

1 

90,000 

182,000 

88,306 

49.5 

3. 

1 

63,200 

110,500 

53,614 

57.2 

60.7 

164.8 

1 

99,000 

204,000 

84,823 

48.5 

3.10 

1 

76,700 

128,600 

53,472 

59.6 

63. 

158.6 

1 

112,300  i  215,000 

76,468 

52.2 

3.75 

1 

90,000 

149,000 

53,100 

60.5 

69.3 

144.2 

1 

116,000 

240,000 

77,947 

Not 

br'k'n 

2 

105,400 

145,950 

47,648 

72.3 

60.8 

164.4 

*  The  tests  marked  *  were  upon  single  links,  the  others  upon  sections  of  cable. 


64 


WROUGHT-mON   AND   CHAIN-CABLES. 


Iron  E. 


CABLE  LINKS. 

ROUND  BARS. 

RATIOS  OF 
LINKS&BAKS. 

i  ! 

Stress  in  Pounds. 

" 

*! 

1 

0 

a 

n 

E 

Stress  in  Pounds. 

«o 

if 

J 

oo 

. 

3    g 

* 

JM 

r3      "S 

f> 

M 

« 

M 

"1  1 

®03  £ 

c  •£ 

g£ 

'Tests  a 

•c  > 
|| 

1 
is 

?  S"  o 

^  <s 

p 

o  . 

'o 

fi 

il 

I] 

I   I 

if 

|J 

I|J| 

Ifi  3 

5  c 

ll 

tn  * 

li 

•i? 

o  Of« 

a  '-  s 

11 

13 

^     K 

E 

£ 

» 

2n 

OQ 

fe 

R 

m 

(2 

23 

& 

M 

4 

43,700 

87,650 

84,360 

49.9 

1 

34,848 

55,152 

53,097  1  63.1 

62.9 

158.9 

4 

44,625  !  113,650 

91,138 

39.3 

1 

28,320 

67,200    53,893 

42.1 

59.2 

169.1 

4 

54,500    134,900 

88,925 

40.4 

1 

39,360 

79,296  ;  52,254 

49.6 

58.8 

170.2 

2 

68,650    160,650 

90,916 

42.7 

1 

50,080 

97,920 

55,415 

59.3 

61. 

164. 

2 

72,250    189,800 

90,991 

38.1 

1 

57,792  |  108,384 

51,940 

53.3 

57.1 

175.1 

ll    91,000  !  221,500 

92,099 

41. 

1 

63,840    124,128  j  51,606 

51.4 

56. 

178.4 

2|    93,800    233,600 

82,858 

40.2 

2 

76,608  |  142,991 

50,880 

53.5 

61.3 

163.2 

Iron  F.    First  Lot. 


28,500 
50,000 
51,000 
60,540 
71,000 
76,400 
83,500 
105,000 

86,400 
101,700 
119,000 
155,500 
174,700 
203,500 
230,900 
268,750 

87,698     33. 
82,855  ;  49.1 
79,545  !  42.9 
88,002  1  38.9 
84,764  !  40.6 
84,615  !  37.5 
83,177  I  36.1 
86,414  !  39.1 

.60 

'!90 
1.00 
1.00 
1.90 
2.4 

3 
2 
2 
2 
2 
2 
2 
2 

32,993 
39,360 
48,190 
56,640 
69,890 
77,520 
91,295 
85,950 

53,053  |  53,850 
64,990    52,970 
77,235  !  51,296 
91,875    51,994 
107,520    52,163 
121,920  |  50,690 
140,925  1  51,039 
152,260  |  48,956 

62.1 
60.5 
62.3 
61.6 
64.9 
63.5 
64.7 
56.4 

61.4 
63.9 
64.9 
59. 
61.5 
59.9 
60.6 
56.6 

162.8 
156.4 
154. 
169.2 
162.5 
166.9 
163.8 
176.5 

Iron  F.     Third  Lot. 


1 

1 

1 
1 

1 
1 

35,600 
47,600 
55,000 
65,600 
70,600 

67,600 
85,000 
107,600 
128,600 
150,500 

84,372 
84,745 
87,693 
85,962 
85,172 

52.6 
56. 
51.1 
.51. 
47. 

• 

2 
2 
2 
2 
2 
2 

31,300 
35,600 
48,600 
58,500 
62.000 
7°  000 

41,600 
50,300 
64,700 
78,300 
89,800 
103  500 

51,921 
50,149 
52,729 
52,339 
50,820 
50  529 

75.2 
70.7 
75.1 
74.7 
69. 
69  5 

61.5 
59.1 
60.1 
60.8 
59.6 

162.4 
168.8 
166. 
164.2 
167.6 

if 
1 

] 
1 

1 

3 
4 
3 
2 
2 
2 

90,000 
90,000 
100,600 
1,533 
3,875 
6,600 
5,800 
10,000 
15,805 



197,600 
215,600 
233,600 
3,775 
8,916 
16,933 
25,400 
34,700 
46,400 

83,095 
78,514 
73,621 
76,003 
80,647 
86,100 
85,519 
74,460 
74,999 

45.5 
41.7 
43. 
40.7 
43.7 
39.1 
20.9 
29. 

• 

2 
2 
2 
1 
4 
1 
3 
3 
3 

85,500 
97,800 
113,800 

'  '4,410 
7,680 
10,834 
16,748 
21,097 

120,200 
136,600 
151,900 
2,919 
5,949 
10,343 
15,924 
23,024 
31,317 

50,547 
49,744 
47,872 
59,585 
54,090 
52,772 
52,051 
50,764 
50,716 

71.2 
71.7 

74.8 

7i!  i 

74.3 
67.9 
72.8 
67.4 

60.8 
63.3 
65. 
77.6 
67.1 
61.2 
62.7 
66.9 
67.7 

164.6 
157.8 
148.8 
129.3 
149.9 
163.7 
159.5 
150.6 
148.1 

Iron  Fx.    First  Lot. 


1 

34,800 

70,300 

86,036 

49.5 

1.12 

5 

27,680 

45,040 

55,770 

61.5 

64. 

156.8 

1 

44,400 

81,400 

79,725 

54.5 

1.42 

5 

35,500 

57,620 

56,434 

61.5 

70.8 

141.2 

1 

6i»100 

111,000 

90,464 

55. 

1.70 

5 

43,100 

68,460 

55,253 

63. 

61.7 

162. 

1 

78,000 

124,000 

82,887 

62.9 

2.25 

5 

50,480 

80,360 

52,968 

64.8 

62.8 

154.2 

1 

80,000 

153,000 

88,593 

52.3 

2.15 

5 

60,620 

94,520 

53,491 

64.1 

61.8 

161.8 

1 

98,000 

168,000 

81,513 

58.3 

3.11 

5 

70,560 

110,140 

53,537 

64. 

65.6 

152.4 

1 

100,000 

185,000 

76,923 

54. 

2.60 

5 

87,960 

129,500 

53,846 

67.9 

70. 

142.8 

1 

110,800 

205,600 

74,063 

53.9 

2.90 

5 

98,920 

146,780 

52,875 

67.3 

71.4 

140. 

1 

117,200 

240,000 

76,384 

Not 

4.8 

5 

108,980 

163,420 

52,011 

66.6 

br'k'n 

*  The  tests  marked  *  were  upon  single  links,  the  others  upon  sections  of  cable. 


THE   CABLE. 


65 


Iron  Fx.     Third  Lot. 


CABLE  LINKS. 

ROUND  BARS. 

RATIOS  OF 
LIN  KS&  BARS. 

h 

£ 

1 

Stress  in  Pounds. 

to  o 
C  c« 

1 

a 

£ 
a 

Stress  in  Pounds. 

Stress- 
Stretch 
e. 

M 

c 

jj 

»     -a 

_ 

• 

.S  es 

« 

^ 

0 

M 

^3      ! 

S  ^ 

r^ 

PQ 

O 

>M 

S  2 

§~ 

»  CQ 

€C 

§ 

§  2.2 

o>  s 

t> 

*0    ^ 

o 
o 

s^ 

1°  "c 

gla 

la 

| 

(/. 

"S    U 

>4!g 

^•s- 

^^ 

0 

h 

2  a! 

Is 

'S^fe 

|i 

o 
£ 

03 

"o 

I? 

|| 

I  ll*^ 

Ir^H 

s-s 

23 

^^ 

IS 

|l 

3  « 

s-2 

Isl 

ii 

la 

s 

X 

S 

£ 

M^     ^ 

X 

fe 

S 

35 

M 

M 

1 

34,500 

69,600 

88,617 

49.6 

2 

28,500 

42,350 

53,915 

67.3 

60.8 

164.4 

1 

1 

39,600 

86,000 

85,724 

46. 

2 

34,800 

54,300 

54,644 

63.5 

63.7 

157. 

£ 

1 

49,000 

105,000 

84,202 

46.7 

2 

41,800 

66,400 

53,247 

62.9 

63.2 

158. 

3 

1 

60,000 

126,800 

83,586 

47.3 

.  .  . 

2 

52,500 

80,000 

52,733 

65.6 

63. 

158.6 

I 

1 

70,600 

152,800 

85,315 

46.2 

.  .  . 

2 

62,400 

94,600 

52,819 

65.9 

61.9 

161.6 

If 

1 

83,000 

179,000 

85,769 

46.4 

2 

70,000 

111,300 

53,329 

62.9 

63.1 

160.8 

IT 

1 

100,000    190,600 

80,237 

52.5 

.  .  . 

2 

81,000 

126,100 

53,154 

64.8 

66.2 

151.2 

2 

1 

1 

109,000  !  229,000 
118,000  ;  238,600 

83,394 
75,938 

47.6 
49.5 

... 

2 

2 

96,200    146,500 
104,500  |  159,500 

53,361 
50,763 

65.7 
65.5 

64. 
66.8 

156.4 
149.6 

Iron  G. 


1 
I 

1 



160,100 
195,200 
215,200 

00,605 
94,118 
89,480 

.... 

.... 

1 
1 
1 

62,600 
69,100 
87,200 

91,800 
106,200 
121,200 

51,958 
51,205 
50,395 

68.1 
65.6 
71.9 

57.3 
54.4 
56.3 

174.4 
183.2 
177.6 

Iron  H. 

\  I 

!!'.!!'. 

170,000 
204,100 
225,200 

96,208 
97,409 
93,638 

1 
1 
1 

53,000 
60,900 
67,000 

92,700 
108,500 
129,400 

52,462 
52,314 
53,800 

57.1 
56.1 
51.7 

54.5 
53.2 
57.5 

183.4 
188. 
174. 

Iron  J. 

11 
i 
i 

'.'.'.'.'.'. 

157,600 
120,000 
222,700 

89,190 
57,859 
92,600 



'.'.'.'.        1 



90,200 
109,400 
128,100 

51,047 
52,748 
53,264 

'.'.'.'. 

57.2 
91.2 
57.5 

174.6 
109.6 
173.8 

II    1 



Iron  K. 

i 
i 
i 
i 

2 
1 

r  1 

39,400 
47,000 
58,000 
57,600 
72,900 
72,500 
97,000 
104,000 

84,500 
96,000 
125,800 
143,000 
177,450 
172,800 
246,800 
258,900 

85,001 
78,240 
84,714 
80,925 
85,559 
71,850 
89,387 
82,400 

46.6 
49. 
42.2 
31.2 
41. 
42. 
39. 
40. 

1.70 
.50 
.47 
.87 
.86 
.65 
1.00 
1.00 

3 

2 
2 

2 

4 
1 
2 

2 

37,120 
44,640 
46,080 
59,040 
72,640 
79,680 
85,680 
101,280 

60,096 
72,960 
82,848 
101,280 
118,463 
139,200 
154,080 
191,520 

60,458 
59,461 
55,790 
57,317 
57,132 
57,874 
55,803 
58,890 

61.7 
61.1 
55.6 

58.2 
63.1 
57.2 
55.6 

52.8 

,71.1 

76. 
65.8 
70.8 
66.8 
80.5 
62.4 
74. 

140.6 
131.4 
150.6 
141.2 
149.7 
124.1 
160. 
135.2 

Iron  L. 

5         1 

i    i 
?    i 

:;;!!! 

193,200 
163,600 
254,600 

109,337 

78,881 
105,862 

II 

50,500 
92,200 
87,200 

123,300 
139,200 
145,000 

69,779 
67,116 
60,291 

41. 

66.2 
60. 

63.8 
85. 
56.9 

156.6 
116.2 
175.6 

.... 

Iron  M. 


u 

li 
i£ 

15 

6 
~6 

53,700 
59,390 
71,700 
(80,000 

117,716 
116,628 
152,467 
125,000 

98,905  45.7 
78,341  !51.4 
86,270  [47.2 
60,270  !64.  | 

'...'. 

20 
115 
162 

10 

54*,789 
61,808 

74  510 

65,960 
83,300 
97,250 

119  750 

53,752 
55,991 
54,480 

57  402 

esis 

62.9 
61  7 

57.3 

72.0 
63.8 

178.4 
140.5 
159.3 

J8 

(79,000 

180,000 

86,788  43.7  j 

*  TJie  tests  marked  *  were  upon  single  links,  the  others  upon  sections  of  cable. 


66 


WKOUGHT-IEON  AND  CHAIN-CABLES. 


Iron  M.    Second  Lot. 


CABLE  LINKS. 

ROUND  BARS. 

RATIOS  OF 
LIN  KS&  BARS. 

-r 

Stress  in  Pounds. 

•£« 

c 

c 

Stress  in  Pounds. 

S-S 

it 

~    C3 

&  « 

^ 

^ 

« 
"s 

1 

f  Tests  avera 

Stretch 
3  observed. 

urc  took 
ce. 

e  by  C'lul 
square 
a  sectional 
\rea. 

11 
I|  . 

sh  of  Unbro 
ks. 

e 

o 

8^ 

Stretch 
s  observed. 

! 

9$ 

quare  inch 
ginal  Area. 

)  between  St 
of  first  Sti 
1  Fracture. 

)  between 
rs  and  Link 

>  between 
iks  and  Ban 

5 

o 
c 

X 

Ig 

Kjj 
|p, 

PI 

c  s  ° 

l"  = 

|S2 

F 

O 

3C-» 
^ 

¥ 

It 

iC 

i5 

|£§ 

i« 

H 

F 

(  92,000 

75,244) 

(63.8 

126.6) 

U 

5 

to 
(114,000 

to 
92,909) 

.... 

.... 

53 



72,700 

59,248 

.... 

to 
(79.0 

to    [ 

156.8) 

(  77,000 

57,650) 

(65.6 

100.3) 

iA 

4 

1      to 
(117,000 

to 
86,474) 

20 



76,800 

56,761 

.... 

to 
(99.7 

to    [ 

152.3) 

n 

3 



(113,100 
to 
(133,000 

76,094) 
to 
89,562) 

.... 

.... 

18 

84,300 

56,777 

.... 

(63.4 

i    to 
(74.6 

134.  ) 
to    [ 
157.7) 

(155,000 

88,058) 

(58.8 

156.4) 

H 

f> 

to 

to 

47 

99  429 

56,270 

!  to 

to    J 

(169,000 

95,642) 

(63.9 

169.9) 

is 

1 



187,000 

90,175 

.... 

.... 

5 



113,760 

54,851 

.... 

60.8 

164.4 

w 

1 



207,000 

92,576 

.... 

.... 

5 



127,700 

57,115 

.... 

61.7 

162.1 

(  212,000 

88,149) 

(60.8 

154.7) 

13 

•> 

to 

to      ( 

29 

137,092 

57,003 

{    to 

to    f 

(  225,600 

93,804) 

(64.7 

164.5) 

(210,000 

81,395) 

(61.4 

147.6) 

1  1.  8 

\ 

1      to 

to      ' 

24 

142,367 

55  181 

\    ^° 

to     ( 

T« 

(228,000 

88,605) 

(67.8167.6) 

(255,000 

81,158) 

(61.7148.6) 

2 

g 

\     to 

to      ( 

47 

171  490 

54  580 

)    to 

to    } 

(278,000 

91,661) 

(67.3 

162.1  ) 

Iron  N. 


1 
1 
1 
1 
1 
1 
1 
1 

45,000 
58,000 
70,100 
80,000 
96,200 
110,300 
116,200 
11S,000 

85,000 
105,000 
126,400 
152,200 
195,500 
201,100 
223,700 
232,000 

84,915 
85,574 
84,492 
87,270 
92,566 
85,538 
81,463 
73,116 

53. 
63.8 
55.4 
52.5 
49.2 
54.8 
51.9 
50.8 

1.76 
2.06 
2.52 
2.77 
3.60 
1.75 
3.40 
2.60 

2 
2 
2 
2 
2 
2 
2 
2 

32,300 
40,800 
50,300 
60,500 
75,800 
80,600 
92,300 
103,000 

56,200 
69,300 
81,200 
93,400 
119,000 
129,350 
140,150 
164,200 

5li,143 
56,478 
54,277 
53,555 
56,344 
55,018 
51,037 
51,748 

57.5 
58.1 
62. 
64.7 
63.6 
62.3 
66.1 
62.6 

66.1 
66. 
64.2 
61.4 
60.9 
64.3 
62.6 
70.8 

151.2 
151.4 
155.4 
162.8 
164.2 
161.8 
159.6 
141.2 

Iron  O. 


31,400 

68,000 

84,872 

46.2 

.. 

1 

30,000 

46,000 

57,363 

65.2 

67.6 

148. 

35,000 

80,900 

85,131 

43.3 

1 

30,800 

50,400 

53,035 

61.1 

62.3 

160.6 

45,800 

95,500 

77,832 

48. 

.. 

1 

36,900 

61,400 

50,040 

60.1 

64.3 

155.6 

51,200 

125,400 

87,631 

40.8 

.. 

1 

50,000 

72,400 

50,594 

69. 

57.7 

173.2 

60,000 

155,500 

86,823 

38.6 

.  . 

1 

58,000 

91,400 

50,919 

63.4 

58.8 

170. 

1 

74,500 

180,000 

87,336 

41.4 

, 

1 

70,100 

108,000 

52,401 

64.9 

60, 

166.6 

1 

90,000 

207,000 

89,070 

43.5 

, 

1 

75,000 

116,500 

50,129 

64.3 

56.3 

177.6 

1 

102,000 

237,000 

87,288 

43. 

. 

1 

83,800 

129,000 

47,478 

65. 

54.4 

183.8 

1 

119,800 

238,000 

75,747 

50.3 

• 

1 

98,700 

151,600 

48,249 

65.1 

63.7 

156. 

THE   CABLE. 
Iron  P. 


67 


CABLE  LINKS. 

ROUND  BARS. 

RATIOS  OF 
LINKS&BAUS. 

1 

Stress  in  Pounds. 

i* 

1 

3 

Stress  in  Pounds. 

*i> 

If 

I* 

.- 

~"£ 

2 

z 

T3 

? 

a 

>d 

—  cs 

mw  « 

rt 

Diameter  of  I 

~ 

X 

1 

"5 
6 

First  Stretch 
was  observe 

Fracture  took 
place. 

£ 

Ratio  betweei 
Stretch,  and 
ture. 

Stretch  of  Unl 
Links. 

Number  of  B 
Test. 

First  Stretch 
was  observe 

| 

o   . 
3  o 

£ 

Per  square  inc 
Original  Art 

l{atio  between 
es  of  first 
and  Fractur 

Ratio  between 
Bars  and  Li 

Ratio  between 
Links  and  B 

1> 

•> 

112,320 

88,612 

2 

45  1°4 

70  704 

55  782 

61  4 

6 

52,800 

110,000 

91,317 

47.6 

.... 

94 

48,550 

74,427 

54,518 

65.3 

.... 

.... 

13 

1 

134  592 

89  968 

1 

46  080 

78  624 

52  556 

58  6 

58  4 

j  7 

fi 

61,800 

141,000 

86,876 

43.8 

2 

89  300 

53  345 

157  9 

Ti16 

1 

134,592 

74,196 

1 

53,760 

95,904 

52,868 

56.1 

71.2 

2 

1 

125,000 

256,320 

80,000 

48.8 

1 

96,000 

159,840 

49,872 

63. 

62.4 

160.4 

Iron  P.     Second  Lot. 


1 

: 

38,000 
45,200 
50,400 
60,000 
.  73,600 
86,000 
106,000 
115,000 
129,000 

60,400 
76,000 
122,100 
118,400 
156,000 
199,000 
212,000 
233,000 
242,000 

78,461 
77,141 
94,871 
76,933 
85,950 
94,270 
86,143 
83,933 
Not  bro 

62.9 
59.5 
43.1 
50.7 
47.2 
43.2 
50. 
49.4 
ken 

'.'.'.'. 

2 
2 
2 

2 
2 

2 
2 
2 

2 

30,200 
40,700 
47,450 
53,500 
60,650 
70,800 
82,400 
89,700 
101,150 

44,500 
56,500 
73,200 
85,000 
98,300 
117,500 
130,050 
145,200 
161,300 

57,807 
57,289 
56,876 
55,230 
54,159 
55,634 
52,844 
52,305 
50,834 

67.9 
72. 
64.8 
62.9 
61.7 
60.2 
63.4 
61.8 
62.7 

73.7 

135.8 

60. 
71.6 
63. 
75.3 
61.3 
62.3 

166.8 
139.6 
158.6 
169.4 
163. 
160.4 

Iron  Px. 


u 

53,000 

116,000 

93,023 

45.7 

....  II     2 

42,300 

70,250 

56,334 

59.5 

60.6 

165.2 

II 

71,400 

156,000 

87,102 

45.8 

2 

62,000 

97,350 

54,354 

64. 

62.4 

160.2 

If? 

84,600 

196,200 

91,003 

43.1 

2 

70,600 

115,500 

54,689 

61.1 

58.8 

169.9 

98,000 

209,800 

86,231 

46.7 

.... 

2 

82,500 

131,900 

54,212 

62.5 

63.1 

158.4 

1* 

108,200 

236,000 

85,943 

45.8 

.... 

2 

88,600 

142,000 

51,762 

62.2 

60. 

166.2 

2 

120,000 

242,000 

Not  bro 

ken 

1 

98,600 

168,800 

53,198 

58.4 

.... 

.... 

68  WROUGHT-IRON  AND   CHAIN-CABLES. 


V-      o 

WlfBBSXTYj 


SECTION   VI. 

PROOF   STRAINS   FOR   CHAIN-CABLES. 

EFFECTS  PRODUCED  BY  THE  USE  OF  THE  STRAINS  PRE- 
SCRIBED BY  THE  ADMIRALTY  PROOF  TABLE.  —  DISCUSSION 
OF  THE  PRINCIPLES  UPON  WHICH  "PROOF  STRAINS" 
SHOULD  BE  BASED.  —  PROOF  TABLE  CALCULATED  UPON 
SUCH  PRINCIPLES. 

A  FINISHED  cable  has  yet  a  final  ordeal  to  undergo  before  it 
is  issued  for  service,  —  one  which  may  prove  disastrous  to  its 
value,  even  if  it  has  escaped  every  danger  that  has  accompanied 
its  manufacture.  It  is  to  be  "  proved  ;  "  which  means  that  each 
of  the  fifteen-fathom  "sections"  of  which  it  is  composed  is  to  be 
subjected  to  a  tensional  strain  sufficient  to  make  it  probable  that 
the  presence  of  any  defective  links  will  be  made  manifest,  that 
they  may  be  removed,  and  replaced  by  others. 

As  tension  in  excess  will  probably  injure  the  cable,  it  becomes 
a  matter  of  importance  to  fix  upon  a  strain  for  each  size,  which, 
while  sufficient  to  insure  the  detection  of  unduly  weak  links, 
will  not  produce  them.  Most  American  manufacturers  of  cable 
use  for  each  size  a  stress  which  is  prescribed  by  the  standard 
proof  table  of  the  British  Admiralty  ;  and  their  cables  are  sold 
with  a  guaranty  that  they  have  been  so  proved. 

Our  experiments  lead  us  to  doubt  the  wisdom  of  thus  apply- 
ing this  English  standard  to  measure  American  material.  We 
consider,  that,  as  applied  to  cables  made  of  American  bar-iron, 
this  standard  is  faulty  in  two  important  respects  :  — 

First,  The  stress  prescribed  by  it  for  every  size  of  cable  is 
too  great. 

Second,  The  stresses  for  the  different  sizes  are  unequal  in 
their  proportion  to  the  strength  of  the  links. 


PROOF   STRAINS  FOR   CHAIN-CABLES. 


69 


And  we  assign  the  following  reasons  for  these  opinions  :  — 

First,  The  stress  for  all  sizes  is  based  upon  the  assumption 
that  the  cable  bolts  of  all  diameters  possess  a  strength  equal 
to  sixty  thousand  pounds  per  square  inch.  Few  bars  of  Ameri- 
can iron  have  this  strength,  and,  when  they  have,  their  cost  pre- 
cludes their  use  as  cable-iron ;  and,  as  has  been  shown  in  the 
investigations  by  tension,  although  this  strength  may  be  found 
in  the  small  bars,  it  is  not  found  in  the  large  sizes  of  the  same 
iron. 

Secondly,  If  the  bars  of  all  sizes  did  possess  this  strength, 
the  "proof"  is  still  too  great;  for  it  probably  exceeds  by  a 
considerable  amount  the  elastic  limit  of  the  links. 

The  table  as  furnished  to  the  committee  by  two  prominent 
manufacturers,  viz.,  Messrs.  J.  B.  Carr  &  Co.  of  Troy,  and  Mr. 
H.  L.  Fearing  of  Boston,  is  herewith  given,  that  the  discussion 
which  follows  may  be  clearly  understood. 


COLUMN  1. 

COLUMN  2. 

COLUMN  3. 

Stress  in 

Stress  in 

Stress  in 

SIZE. 

Tons. 

Pounds. 

Tons. 

Pounds. 

Tons. 

Pounds. 

1  " 

18 

40,320 

18 

40,320 

18 

40,320 

i"A 

20 

44,800 

20 

44,800 

20.32 

45,517 

if 

23 

51,520 

23 

51,520 

22.78 

51,030 

4 

26 

58,200 

25 

55,960 

25.38 

56,857 

4 

28 

62,720 

29 

64.960 

28.12 

63,000 

ift 

30 

67,200 

31 

69,440 

31.01 

69,457 

4 

34 

76,160 

34 

76,160 

34.03 

76,230 

ifi 

37 

82,880 

37 

82,880 

37.22 

83,317 

ij 

41 

91,800 

41 

91,800 

40.50 

90,720 

!T96 

44 

98,500 

43 

96,320 

43.94 

98,437 

If 

48 

107,520 

48 

107,520 

47.53 

106,470 

ifl 

52 

116,480 

51 

114,240 

51.25 

114,817 

If 

56 

125,440 

56 

125,440 

55.12 

123,480 

1|| 

60 

134,400 

59 

132,160 

59.05 

132,275 

li 

64 

143,360 

64 

143.360 

63.38 

141,750 

ill 

68 

152,320 

68 

152,320 

67.57 

151,357 

2 

72 

161,280 

72 

161,280 

72 

161,280 

2& 

. 

... 

76 

171,360 

76.59 

171,517 

4 

80 

179,200 

81.3 

181,120 

81.28 

182,070 

2A 

86.13 

192,937 

W 

88 

197,120 

91.1 

204,064 

91.11 

204,120 

70 


WKOUGHT-IRON  AND   CHAIN-CABLES. 


The  formula  upon  which  column  3  is  calculated  is  one 
embodied  as  a  rule  as  follows :  — 

"  For  proof  of  each  size,  square  the  number  of  eighths  of  an 
inch  in  the  diameter  of  the  bar,  and  multiply  the  result  by  630," 
the  result  being  the  stress  in  pounds.  Thus  :  1",  8  eighths, 
squared  =  64,  and  64  X  630  =  40,320  pounds." 

Our  experiments  show  that  the  elastic  limit  of  the  large  bars 
is  generally  lower  than  that  of  the  small  ones  of  the  same  iron. 
Hence  the  irregular  effect  of  the  proof  strains  becomes  a  danger- 
ous one. 

The  practical  and  actual  results  which  we  have  found  to 
occur  through  the  use  of  this  table,  and  which  have  doubtless 
occurred  with  many  cables  proved  by  it,  but  which  have  not 
been,  found,  are  that  the  stress  is  so  great  that  it  always  exceeds 
the  elastic  limit  of  the  links,  and  frequently  cracks  them. 

A  few  such  results  will  be  given.  Six  sections,  each  five  fath- 
oms in  length,  were  made  up  from  good  chain-iron ;  three  were 
of  1|",  and  three  of  1|":  all  were  "proved  "  by  the  Admiralty 
Table,  and  after  proof  inspected  in  the  shop ;  all  were  "passed  " 
as  sound;  but  upon  examination  by  aid  of  a  magnifying-glass 
fourteen  of  the  387  links  were  found  to  be  cracked. 

In  the  following  table  the  strength  of  the  strongest  and 
weakest  links  made  from  several  of  the  best  of  the  chain-irons 
we  have  examined  is  given,  with  the  ratio  borne  to  such 
strength  by  the  Admiralty  proof  strains  for  the  sizes :  — 


IRON. 

STRENGTH  OP  LARGE 
LINKS. 

ADMIRALTY 
PROOF, 
PERCENTAGE 

OF 

STRENGTH  OF  SMALL 
LINKS. 

ADMIRALTY 
PROOF, 

PERCENTAGE 
OF 

1 

53 

Strongest. 

Weakest. 

Strongest. 

Weakest. 

« 
.2 

02 

Strongest. 

Weakest. 

Strongest. 

Weakest. 

A.. 
C.. 
D.. 
F.. 
N.. 
O.. 
P.. 

2 

1 

! 

1 

1 

it 

\ 

Pounds. 
283,000 
231,300 
215,000 
215,600 
225,700 
237,000 
233,000 

Pounds. 

248  000 
191000 

57 
53 
66 
66 
63.3 
60 
60.8 

65 
64 

f" 

u 
II 

Pounds. 
72,670 
96,960 
79,200 
67,600 
85,600 
68,000 
122,100 

Pounds. 
69  600 

74488 

55.5 
52.5 
51.3 
59.6 
60 
59.3 
51.2 

58 
65 

61.6 

61. 

64.5 

55.6 

PKOOF   STRAINS   FOR   CHAIN-CABLES.  71 

Convinced  by  the  evidence  which  has  been  given,  that  prov- 
ing American  cables  by  this  standard  was  a  fruitful  source  of 
weakened  cables,  we  were  also  aware,  that,  in  recommending 
that  it  should  be  no  longer  used,  we  should,  if  the  advice  were 
followed,  deprive  manufacturers  of  good  cables  of  a  safeguard 
against  competition  by  those  who  might  unchecked  use  inferior 
iron.  We  have  therefore  considered  it  essential  that  we  should 
provide  a  substitute  which  would,  in  our  judgment,  prescribe 
strains  which  would  fully  prove  cables,  and  not  be  liable  to 
injure  them.  We  submit  such  a  table,  which  is  based  upon  the 
two  principles,  that  a  proof  strain  should  not  greatly  exceed 
the  elastic  limit,  and  that  the  strength  of  a  cable  is  equal  only 
to  that  of  its  weakest  link.  In  the  preparation  of  this  table  it 
was  first  necessary  for  us  to  establish  within  reasonable  limits 
the  probable  maximum  and  minimum  strength  of  cables  of 
various  sizes,  and  the  elastic  limit  of  the  links.  Neither  of 
these  factors  can  be  fixed  definitely:  there  are  many  causes 
which  tend  to  produce  great  differences,  both  in  the  strength 
and  elastic  limit  of  links  made  from  the  same  bar.  The  most 
important  of  these  causes  is  the  liability  of  the  welds,  which 
at  the  best  are  the  weak  spots  of  all  links,  to  lack  uniformity ; 
and  no  rules  can  be  given  which  will  insure  uniform  work  from 
a  number  of  chain-welders.  We  were  therefore  compelled  to 
base  our  table  upon  data  which,  at  the  best,  could  be  considered 
as  but  indicating  probabilities. 

Assuming  as  a  standard  of  perfection  the  characteristics  of  a 
bar,  which  when  made  into  a  link  should  develop  twice  the  origi- 
nal strength  of  the  bar,  we  considered  that  the  iron  which  ap- 
proached most  closely  and  with  uniformity  this  standard  was 
that  which  should  be  considered  as  the  most  suitable  for  cables. 
We  have  the  records  of  the  strains  at  which  a  large  number  of 
bars  in  their  normal  condition  were  ruptured  by  tension,  and  of 
many  sections  of  cable  made  from  them,  which  are  incorporated 
in  the  "Tables  of  Comparative  Action  of  Bars  and  Links." 
From  these  tables  we  have  made  the  following  abstracts  which 
enable  us  to  arrive  at  conclusions  as  to  the  probable  strength 
of  cables  made  from  irons  varying  in  characteristics :  — 


WROUGHT-IRON   AND   CHAIN-CABLES. 


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74  WROUGHT-IRON  AND   CHAIN-CABLES. 

We  have  the  comparative  records  of  210  sections  of  cables 
broken  by  tension,  which  were  made  of  fifteen  different  irons. 
Assuming  that  the  utmost  strength  which  can  be  found  in  a 
link  is  equal  to  200  per  cent  of  that  of  the  bar  from  which  it 
was  made,  we  have  a  standard  by  which  to  compare  the  irons, 
and  establish  their  relative  value.  Examining  the  abstracts  by 
this  standard,  we  find  that  36  sections  developed  over  170  per 
cent  of  the  bar's  strength,  22  of  them  exceeded  175  per  cent, 
9  exceeded  180  per  cent,  and  only  one  exceeded  185  per  cent. 

On  the  other  hand,  67  sections  developed  less  than  155  per 
cent,  leaving  107,  or  over  50  per  cent  of  the  series,  which 
developed  between  155  and  170  per  cent  of  the  bar's  strength ; 
and  of  these  the  average  development  was  163  per  cent. 

The  210  sections  of  various  irons  can  be  reduced  to  143  sec- 
tions of  iron  which  may  be  considered  as  more  or  less  suitable 
for  cable,  by  eliminating  the  records  of  the  67  sections,  which 
were  broken  at  less  than  155  per  cent  of  the  bar's  strength,  and 
at  once  deciding  that  they  have  no  claim  to  be  considered  as 
having  been  made  from  suitable  chain-iron. 

This  we  can  do  in  many  cases,  and  assign  good  reasons :  24 
sections  were  made  from  an  iron  (M)  in  which  analysis  demon- 
strated that  phosphorus,  copper,  nickel,  and  in  some  cases 
chromium,  occurred,  and  possibly  reduced  their  welding  values, 
as  all  the  "  low  breaks "  of  this  iron  occurred  "  through  the 
weld ; "  eight  were  made  from  iron  K,  in  which  carbon  was  high, 
and  ten  from  irons  Fx  and  P,  which  were  known  to  have  been 
overworked,  leaving  but  22  such  percentages  to  be  assigned  to 
the  chapter  of  accidents.  From  which  data  we  conclude  that 
bars  of  fairly  good  chain-iron  will  produce  links  whose  strength 
will  not  be  less  than  155  per  cent,  and  not  over  170  per  cent; 
and  that  by  a  series  of  tests  an  average  of  not  less  than  163  per 
cent,  made  up  of  fairly  uniform  factors,  should  be  expected. 

We  have  §therefore  adopted  for  our  standard  of  strength  and 
welding  qualities  combined,  170  per  cent  of  the  strength  of  the 
bar  for  a  maximum,  163  per  cent  for  an  average,  and  155  per 
cent  for  a  minimum.  Iron  which  in  the  link  form  develops  the 


PROOF   STRAINS  FOR   CHAIN-CABLES.  75 

average,  by  results  which  do  not  vary  greatly,  we  consider  to  be 
suitable ;  that  which  falls  below  the  average,  or  produces  it  by 
very  irregular  factors,  we  consider  as  unsuitable. 

It  remains  to  decide  upon  the  strength  of  bar,  which  will 
most  probably  produce  links  which  will  develop  the  largest  and 
most  uniform  percentages.  Our  records  again  supply  the  re- 
quired data.  We  find  the  irons  A,  B,  O,  and  F,  which  were  low 
in  tensile  strength,  sustained  the  process  of  manufacture  into 
links  with  less  loss  of  strength  than  did  other  irons  which 
exceeded  in  this  respect ;  and  with  all  of  the  series  excess  of 
tensile  strength  was  accompanied  by  deficiency  in  strength  and 
uniformity  as  cable. 

We  have  therefore  decided  upon  adopting  a  low  tensile  strength 
as  a  probable  indication  of  a  high  welding  value,  and  as  shown 
by  the  relative  order  as  judged  by  the  power  of  resisting  sud- 
den strains,  of  great  resilience. 

In  selecting  the  low  tensile  strength,  we  did  not  decide  arbi- 
trarily in  favor  of  the  precedence  which  should  be  given  to  the 
percentage  of  bar's  strength  developed  by  the  links.  We  find 
that  in  many  cases  the  actual  strength  of  the  links  made  from 
the  bars  of  low  tensile  strength  equals  and  exceeds  that  of 
others  from  much  stronger  bars. 

For  example,  iron  K  2"  bar,  tensile  strength  58,900  pounds 
per  square  inch ;  strength  of  link,  258,900  pounds. 

Iron  A,  tensile  strength  2"  bar,  50,171  pounds ;  strength  of 
link,  265,000  pounds. 

Iron  D,  tensile  strength  2"  bar,  51,152  pounds ;  strength  of 
link,  276,500  pounds. 

Iron  F,  tensile  strength  2"  bar,  48,956  pounds ;  strength  of 
link,  268,750  pounds. 

In  recommending  for  cable-manufacture  iron  of  this  character, 
we  are  aware  that  in  so  dping  we  will  come  in  contact  with  a 
widely-spread  and  deeply-rooted  prejudice  in  favor  of  the  strong 
bar  as  best  adapted  to  make  strong  links.  It  undoubtedly  would 
be  so,  were  it  not  that  great  strength  in  the  direction  of  the 
fibre  is  not  found  often  to  exist  except  through  the  effect  of 


76  WROUGHT-IRON  AND   CHAIN-CABLES. 

a  great  amount  of  work,  which  will  cause  the  iron  to  be  too 
expensive  for  cable-iron,  or  through  the  presence  of  various 
chemicals  which  increase  tenacity  at  the  expense  of  welding 
properties,  thus  unfitting  it  for  use  as  cable-iron. 

We  consider  that  our  experiments  justify  us  in  recommend- 
ing as  a  suitable  strength  for  a  2"  bar  of  chain-iron  a  mean 
between  the  margins  found  to  exist  in  those  bars  whose  record 
both  in  bar  and  link  form  has  been  just  given  ;  and  as  the  links 
of  iron  D,  with  tensile  strength  51,152  pounds,  and  of  iron  F 
with  48,956  pounds,  were  equally  good  and  strong,  we  adopt 
their  mean  of  50,000  pounds.  And  we  find  that  iron  A,  which 
possesses  nearly  the  medium  strength  as  a  bar  (50,171  pounds), 
produces  cable  which  is  remarkably  strong  and  uniform. 

Considering,  then,  that  an  iron  is  suitable,  which,  as  a  2"  bar, 
has  strength  of  50,000  pounds  per  square  inch,  and  that  other 
irons  whose  variation  from  this  strength  does  not  exceed  five  per 
cent  above  or  three  per  cent  below  are  equally  suitable,  we  have, 
in  determining  the  strength  for  the  other  sizes,  to  avail  ourselves 
of  the  information  procured  in  the  investigation  of  the  action  of 
the  rolls ;  which  is,  in  brief,  that  the  proportional  strength  of  the 
bars  of  the  same  material  increases  as  the  diameter  decreases, 
and  that  the  aggregate  of  the  increase  for  the  sixteen  sizes  (meas- 
uring by  sixteenths  of  an  inch  between  2"  and  V)  is  from  four 
to  six  thousand  pounds,  produced  by  steps  which  are  made 
more  or  less  irregular  by  irregularities  in  heating  the  piles. 

Using  the  mean  of  the  aggregate  of  increase  of  our  best  and 
most  uniform  irons,  we  find  that  the  strength  per  square  inch 
of  a  bar  of  V  diameter  is  about  5,600  pounds  greater  than  that 
of  the  2",  and  that,  if  the  2"  bar  is  equal  to  50,000  pounds,  it  is 
probable  the  V  will  be  equal  to  55,600  pounds. 

It  was  necessary  to  connect  these  strengths  assigned  to  the 
extremes  by  a  series  of  successively  increasing  factors,  the  aggre' 
gate  of  which  should  equal  5,600  pounds.  It  was  evident  that 
a  uniform  co-efficient  of  increase  for  each  of  the  sixteen  reduc- 
tions could  not  be  used,  as  the  difference  in  strength  produced  by 
variations  in  reductions  changed  much  less  rapidly  than  did  that 


PROOF   STEAINS   FOR   CHAIN-CABLES. 


77 


in  the  entire  strength  of  the  various-sized  bars  produced  by 
variations  in  diameter.  We  therefore  calculated  a  ratio  which 
produced  a  constantly  increasing  co-efficient  to  be  applied  as 
the  diameters  decreased,  with  the  results  given  in  the  table 
below ;  each  of  which  results  is  the  correction  to  be  added  to 
the  strength  per  square  inch  of  any  size  in  order  to  obtain  that 
of  the  size  -Jg"  less  in  diameter. 

Starting  with  50,000  pounds  as  the  strength  of  the  2",  and 
adding  the  increasing  co-efficient,  we  arrive  at  a  strength  per 
square  inch  for  each  size  which  agrees  closely  with  that  found 
in  the  best  and  most  uniform  chain-irons.  The  latter,  however, 
being  exposed  to  constant  chances  of  irregularities  from  many 
causes,  cannot  be  expected  to  coincide  in  strength  very  closely 
with  any  calculated  table. 

Using  the  above  factors  of  correction,  we  obtain  the  following 
table :  — 

Probable  Strength  of  Round  Bars,  calculated  with  an  Allowance  for  Variation  in 
Strength  due  to  Variation  in  Diameter. 


STRENGTH  or  BAR. 

STRENGTH  OF  BAR. 

Size  of 
Bar. 

Per  Square 

Coefficient 

Of  Entire 

Size  of 
Bar. 

Per  Square 

Coefficient 
,.f 

Of  Entire 

Inch. 

Increase. 

Bar. 

Inch. 

Increase. 

Bar. 

Pounds. 

Pounds. 

Pounds. 

Pounds. 

Pounds. 

Pounds. 

2   " 

50,000 

245 

157,080 

1* 

52,584 

357 

85,339 

Hi 

245 

253 

148,137 

If 

941 

376 

78,607 

H 

498 

262 

139,430 

iJv 

53,317 

398 

72,133 

Mf 

760 

273 

130,966 

4 

715 

423 

65,914 

if 

51,033 

284 

122,745 

4 

54,138 

451 

59,958 

Ml 

317 

296 

114,770 

4 

589 

484 

54,261 

if 

613 

309 

107,040 

4 

55,073 

523 

48,8QO 

ift 

922 

323 

99,560 

i 

596 

.    . 

43,665 

4 

52,245 

339 

92,322 

Accepting  this  rate  of  increase  of  strength  as  one  which  ap- 
proximates to  the  actual  increase  of  tenacity  of  iron  bars  of 
decreasing  diameter,  we  have  used  it  in  the  calculation  of  our 
proof-table. 

A  few  examples  will  be  given,  which  show  conclusively  that, 


78 


WBOUGHT-IKOX  AXD   CHAIN-CABLES. 


by  means  of  the  corrections  for  variation  in  diameter  given  in 
the  table,  the  strength  of  a  bar  of,  say,  2",  can  be  closely  esti- 
mated from  the  data  furnished  by  the  test  of  V  bar.  Selecting 
irons  A,  F,  O,  and  P,  which  were  quite  uniform,  the  strength 
of  the  2"  bars  was :  — 


Actual  strength A,  157,630  Ibs. ;  F,  150,413  Ibs. ;  0, 151 ,597  Ibs. 

Calculated  with  correction A,  154,190  Ibs. ;  F,  151,346  Ibs. ;  O,  148,989  Ibs. 

Calculated  without  correction A,  181,836  Ibs. ;  F,  163,136  Ibs. ;  0, 166,635  Ibs. 


P,  159,720  Ibs. 
P,  163,800  Ibs. 
P,  181,600  Ibs. 


The  latter  process  involving  an  over-estimate  of  from  12,700 
to  24,200  pounds ;  which  error  is  reduced  in  two  cases  by  the 
use  of  the  corrections  to  an  over-estimate  of  4,080  and  933 
pounds,  and  in  others  to  an  under-estimate  of  3,448  and  2,608 
pounds. 

The  following  table  has  been  prepared,  in  which  the  aver- 
age strength  of  such  bars  as  have  produced  good  cables  is 
placed  in  contrast  with  the  strength  called  for  by  the  calcu- 
lated table :  — 

Comparison  of  Calculated  with  Actual  Strength  of  Bars. 


Strength. 

Irons  represented  in  Averages. 

Size 

TliflFVu. 

of 
Bar. 

Calcu- 
lated. 

By  actual 
Tests. 

uiner- 
ence. 

No. 
of 
Irons. 

No. 
of 

Tests. 

Name  of  Irons. 

Pounds. 

Pounds. 

Pounds. 

2  " 

157,080 

157,580 

500 

9 

35 

A,  C,  D,  E,  F,  Fx,  M,  O,  P. 

if! 

148,137 

1$ 

139,430 

141,120 

1,690 

9 

26 

Same  as  2". 

m 

130,966 

131,975 

1,009 

5 

8 

B,  C,  E,  G,  H. 

H 

122,745 

124,580 

1,835 

13 

33 

A,  C,  D,  E,  F,  G,  H,  J,  Fx,  O,  N,  P,  M. 

it* 

114,770 

115,690 

920 

4 

7 

B.C.E,  G. 

if 

107,040 

108,800 

1,760 

10 

25 

A,  C,  D,  E,  F,  Fx,  G,  H,  J,  O. 

1A 

99,560 

if 

92,322 

93,358 

1,036 

13 

34 

Same  as  IjJ". 

if 

85,339 
78,607 

85,000 
79,311 

339 
704 

6 
9 

12 

27 

B,  C,  E,  G,  H,  P. 

A,  C,  D,  E,  F,  Fx,  N,  O,  P. 

1^- 

72,133 

74,505 

2,372 

»  1 

94 

P. 

H 

65,914 

66,724 

810 

9 

106 

Same  as  If". 

"1    3 

59,958 

jF 

54,261 

54,570 

309 

9 

29 

Same  as  lj{". 

iTig 

48,800 

43,665 

44,126 

461 

6 

26 

A,  D,  F,  Fx,  O,  P. 

PKOOF   STRAINS  FOE   CHAIN-CABLES. 


Having  thus  fixed  upon  a  suitable  strength,  for  each  sized 
bar,  we  deduce  the  probable  strength  of  cables  made  from 
them  by  the  aid  of  the  percentages  of  the  bar's  strength  which 
we  have  found  will  probably  be  developed  by  the  links,  as 
indicated  by  those  found  in  such  irons  as  we  have  examined. 

In  this  table  of  strength  of  links  it  is  considered  that  no  iron 
should  be  expected  to  possess  in  link  form  over  170  per  cent  of 
the  bar's  strength,  and  that  no  suitable  chain-iron  should  possess 
less  than  155  per  cent  of  the  same ;  and  that  the  average  strength 
of  a  number  of  tested  sections  should  not  be  less  than  163  per 
cent,  such  average  to  be  made  from  fairly  uniform  factors. 

Probable  Strength  of  Cables   made  from  Bars  with   Strength  corresponding  to 
that  given  in  Table. 


Size  of  Bar. 

Strength  of  Entire 
Bar. 

Maximum, 
170  per  cent  of  Bar. 

Average, 
163  per  cent  of  Bar. 

Minimum, 
155  per  cent  of  Bar. 

Pounds. 

Pounds. 

Pounds. 

Pounds. 

2" 

157,080 

267,036 

256,040 

243,474 

i| 

148,137 

251,833 

241,463 

229,612 

, 

139,430 

237,031 

227,271 

216,116 

Ml 

130,966 

222,642 

213,475 

202,997 

if 

122,745 

208,666 

200,074 

190,255 

Hi 

114,770 

195.109 

187,075 

177,894 

if 

107,040 

181,968 

174,475 

165,912 

i^9g 

99,560 

169,250 

162,283 

154,318 

14 

92,322 

156,947 

150,485 

143,099 

1 

85,339 

'    78,607 

145,076 
133,632 

139,103 
128,129 

132,275 
121,841 

72,133 

122,626 

117,577 

111,806 

ii 

65,914 

112,054 

107,440 

102,167 

^13& 

59,958 

101,929 

97,731 

92,935 

M 

54,261 

92,244 

88,445 

84,105 

4 

48,800 

82,960 

79,544 

75,640 

1. 

43,665 

74.230 

71,172 

67,681 

We  have  concluded  that  we  cannot  adopt  a  safer  proof-strain 
than  one  Which  approximates  to  the  elastic  limit  of  the  link ; 
and  the  link  whose  elastic  limit  we  should  adopt  is  the  weakest 
one  which  will,  after  proof,  remain  in  the  cable. 

We  have  found  by  a  great  number  of  tests  of  bars  in  their 


80  WROUGHT-IKON  AND   CHAIN-CABLES. 

normal  condition,  that  the  elastic  limit  of  good  cable-iron  is 
about  57  per  cent  of  its  ultimate  strength. 

The  process  by  which  the  links  are  manufactured  undoubt- 
edly changes  both  the  strength  and  elastic  limit  of  the  portion 
upon  which  the  welds  are  made  :  the  extent  of  this  change  we 
have  no  means  of  knowing ;  and  so  irregular  are  the  processes 
of  manufacture,  that,  if  accurately  ascertained  in  regard  to  a 
tested  link,  the  data  would  be  of  no  value  in  estimating  its 
extent  in  the  case  of  another. 

We  are  therefore  again  reduced  to  probabilities.  Generally 
the  elastic  limit  of  material  is  coincident  with  the  first  percep- 
tible permanent  change  of  form  produced  by  stress.  With  a 
chain-link  this  cannot  be  accepted  as  correct,  as,  through  vari- 
ous causes,  the  form  of  the  link  may  change  at  a  stress  not 
great  enough  to  produce  change  in  the  atomic  relations  of  the 
material.  Still,  this  first  change  of  form  indicates  an  approach 
to  this  limit ;  and  we  have  carefully  observed  it  in  the  test  of 
many  links,  and  find  that  with  such  irons  as  A,  B,  C,  F,  Px, 
and  others  considered  suitable  for  cable,  the  percentage  of  the 
stress  which  will  break  the  cable,  at  which  the  elongation  can 
be  observed  and  measured,  is  about  44  per  cent,  and  that  this 
percentage  exists  with  considerable  regularity,  so  much  so  that 
we  feel  justified  in  assuming  it  as  the  nearest  approximation  to 
the  elastic  limit  of  the  link  that  can  be  deduced  from  our  ex- 
periments. But  we  believe,  for  several  reasons,  that  in  most 
cases  it  is  too  low  a  percentage  :  first  of  which  is,  that,  through 
badly  fitting  studs,  many  links  during  the  beginning  of  an  in- 
creasing stress  may  be  considered  as  open  or  unstudded  ones, 
and  the  "  first  stretch  "  is  produced  by  a  slight  closure  of  the 
sides  upon  the  stud ;  and  open  links  begin  to  stretch  at  a  much 
lower  stress  than  studded  ones.  It  is  probable  that  a  mean  be- 
tween the  ratios  of  the  ultimate  strength  at  which  the  material 
in  bar  form  begins  to  stretch,  viz.,  57  per  cent,  and  that  at 
which  the  links  first  elongate,  viz.,  44  per  cent,  will  give  as 
nearly  the  probable  elastic  limit  of  the  link  as  can  be  obtained 
by  any  other  process.  No  exact  limit  can  be  fixed  upon. 


PEOOF   STRAINS   FOB   CHAIN-CABLES. 


81 


We  have,  therefore,  in  calculating  the  proof-strains,  assumed 
that  it  is  not  safe  to  use  above  50  per  cent  of  the  strength  of 
the  weakest  part  of  the  cable. 

The  proving  strains  calculated  upon  the  principles  indicated 
are  as  follows  :  — 

Recommended  Proof-Table:  being  equal  to  45.57  per  cent  of  the   Strength  of 
the  Strongest,  and  to  #0  per  cent  of  that  of  the  Weakest,  Links. 


SIZE. 

PROVING  STRAIN. 

SIZE. 

PROVING  STRAIN. 

Inches. 

2 

if  •     ' 

if  ;  ; 

if6  .  . 

Pounds. 
121,737 
114,806 
108,058 
101,499 
95,128 
88,947 
82,956 
77,159 
71,550 

Tons. 

5l|| 

Inches. 

\'      ' 

H'  ' 

4\  ; 

i16.  . 

Pounds. 
66,138 
60,920 
55,903 
51,084 
46,468 
42,053 
37,820 
33,840 

Tons. 
onll78 

97_*_10- 
^'  2240 
0/1  2143 

toiH 

^-2240 

39|ff-J 

-'12240 
001804 
2240 

isilii 

-l°2240 
1fil980 

342^ 

XU2240 
IK  240 

i*  ;  . 

102240 

2240 

Comparison  of  the  Proving  Strains  recommended,  and  Strains  in  Use. 


SIZE  or 
CABLE. 

RECOMMENDED 
PROVING 

STRAIN. 

PROBABLE  PERCENT- 
AGE OF  STRENGTH 

OF  — 

ADMIRALTY 
PROVING 
STRAIN. 

PROBABLE  PERCENT- 
AGE OF  STRENGTH 

OF  — 

Strongest 
Link. 

Weakest 
Link. 

Strongest 
Link. 

Weakest 
Link. 

Inches. 

Pounds. 

Pounds. 

9 

121,737 

45.5 

50 

161,280 

60.3 

66.2 

!}*•     '     • 

114,806 

45.5 

50 

151,357 

60.1 

65.9 

11   ... 

108,058 

45.5 

50 

141,750 

59.8 

65.5 

Ml-    -    « 

101,499 

45.5 

50 

132,457 

59.4 

65.2 

if  .    .    . 

95,128 

45.5 

50 

123,480 

59.1 

64.9 

111.    .    . 

88,947 

45.5 

50 

114,817 

58.8 

64.5 

if  •    •    • 

82,956 

45.5 

50 

106,470 

58.5 

64.1 

1A.     .     . 

77,159 

45.5 

50 

98,437 

58.2 

63.7 

71,550 

45.5 

50 

90,720 

57.8 

63.3 

lT7g.     .     . 

66,138 

45.5 

50 

83,317 

57.4 

62.9 

1^.   . 

60,920 

45.5 

50 

76,230 

57.0 

62.5 

!A-    •    • 

55,903 

45.5 

50 

69,457 

56.6 

621 

46.  .  . 

51,084 

45.5 

50 

63,000 

56.2 

61.6 

Ife-     •     « 

46,468 

45.5 

50 

56,857 

55.7 

61.1 

it   •     •     • 

42,053 

45.5 

50 

51,030 

55.3 

60.6 

1TV-    .    . 

37,820 

45.5 

50 

45,517 

54.8 

60.1 

1    .   .  . 

33,840 

45.5 

50 

40,320 

54.3 

59.5 

82  WKOUGHT-IKON  AND  CHAIN-CABLES. 

The  important  points  of  difference  between  the  recommended 
table  and  the  one  in  use  are :  — 

First,  In  the  former,  the  proof  stress  is,  for  every  size,  uni- 
form in  its  proportion  to  the  probable  strength  of  the  links ;  in 
the  latter,  it  varies  with  every  change  of  size. 

Second,  Unless  £he  elastic  limit  of  the  link  is  a  greater  pro- 
portion of  its  ultimate  strength  than  that  of  the  bar  was  of  its 
strength,  the  strains  of  the  table  in  use  exceed  this  limit  greatly, 
upon  all  sizes,  while  those  of  the  former  do  not. 

Third,  The  recommended  table  recognizes  the  probability 
of  there  being  introduced  into  cables  links  made  from  bars 
which,  although  of  equally  good  iron  as  the  rest,  are,  through 
fault  in  rolling,  more  or  less  scant,  and,  in  consequence,  possess 
less  strength  than  bars  rolled  true ;  which  deficiency  will  be 
carried  into  the  links.  Should  there,  by  accident,  be  a  few 
links  of  1-J-f  "  in  a  2"  cable,  the  Admiralty  proof  would  strain 
the  strongest  of  such  links  to  over  62  per  cent,  and  the  weakest 
to  over  70  per  cent,,  of  the  actual  strength. 

For  these  reasons  we  recommend  that  this  table,  based  upon 
actual  strength  of  American  iron,  be  used  in  place  of  that  of 
the  Admiralty.  • 


NOTES   UPON  THE  IRONS  EXAMINED.  83 


SECTION  VII. 

PART  I.  —  Notes  upon  the  Various  Irons  examined,  with  Experiments  showing 
Effects  produced  by  reworking  Material  of  Different  Characteristics.  PART 
II.  —  Chemical  Analyses  of  the  Irons,  ivith  Comparison  of  the  Chemical  and 
Physical  Results. 

PART  L  — NOTES  UPON  THE  IRONS  EXAMINED. 

A  COMPARISON  of  the  results  obtained  by  steady  and  sudden 
strains  upon  bars,  and  by  steady  strains  upon  the  links  made 
from  the  bars,  indicates  there  are  two  classes  of  iron,  which, 
although  possessing  considerable  tensile  strength  in  the  form 
of  straight  bars,  are  equally  unsuitable  for  cable-iron,  through 
defective  resilience,  or  inferior  welding  qualities. 

The  first  class  includes  the  greater  portion  of  the  ordinary 
cheap  iron  found  in  the  market,  which  is  cheap  because  it  has 
not  received  enough  work  which  is  expensive,  to  greatly  change 
its  characteristics  from  those  which  it  possessed  as  crude  iron. 

When  tested  by  tension,  iron  of  this  class  shows  slight  change 
of  form  at  rupture  ;  and  when  broken  by  impact  it  proves  brit- 
tle and  unreliable. 

After  fracture  the  appearance  of  the  broken  surface  is  de- 
scribed as  "  coarse  granulous,"  and  generally  is  bright  and 
glistening. 

Such  iron  will,  when  subjected  to  impact,  break  with  but 
little  deflection,  and  sometimes  by  blows  of  less  force  than  it 
had  previously  withstood  without  sign  of  injury. 

The  second  class  includes  many  excellent  irons  with  high 
tenacity,  which  is  due  either  to  very  thorough  work,  or  to  in- 


84  WROUGHT-IRON   AND   CHAIN-CABLES. 

gredients  in  its  composition  which  tend  to  increase  tenacity, 
frequently  at  the  expense  of  welding  qualities. 

A  few  notes  in  regard  to  the  irons  we  have  examined  will 
illustrate  these  points. 

CONTRACT  CHAIN-IRON. 

The  general  character  of  this  iron  was  that  of  class  first, 
coarse,  brittle,  and  slightly  worked. 

As  a  result  of  the  tests  the  entire  stock  on  hand  was  con- 
demned ;  but  much  of  it  having  been  found  to  be  susceptible  of 
great  improvement  by  re-working,  it  was  so  treated  with  good 
results. 

HAMMERED  IRON. 

The  process  by  which  this  iron  was  manufactured  was  as 
follows :  — 

Such  of  the  contract  chain-iron  as  our  experiments  had  shown 
to  be  most  benefited  by  increased  work  was  selected,  heated  to 
a  very  high  heat,  and  thoroughly  hammered  by  the  steam-ham- 
mer, each  link  or  bolt  by  itself,  until  it  was  flattened  to  a  slab. 
During  the  process  great  quantities  of  dross  and  .scoria  were 
expelled. 

Old  condemned  boilers  were  cut  up,  and  the  better  portions 
cut  into  slabs,  which  were  heated  to  a  red  heat,  and  the  rust 
beaten  off.  These  slabs  of  the  two  irons  were  then  piled  in  the 
following  manner :  — 


Boiler-iron. 


Twice-hammered  chain-iron. 


Once-hammered  chain-iron. 


Crown-sheet  boiler-iron. 


Once-hammered  chain-iron. 


Twice-hammered  chain-iron. 


Boiler-iron. 


NOTES   UPON   THE   IRONS   EXAMINED.  85 

These  piles  were  about  20"  by  10",  and  were  heated  and  ham- 
mered into  octagonal  irons. 

The  advantages  which  it  was  hoped  would  be  secured  by  the 
above  method  of  piling  were,  that  the  soft  and  comparatively 
plastic  centre  would  permit  extreme  flexure ;  that  the  coarse, 
once-heated  chain-iron  would,  being  supported  by  this  yielding 
centre,  sustain  flexure  to^a  much  greater  extent  than  if  not  so 
supported ;  and  that  the  thoroughly  re-heated  and  re-worked 
layers  of  chain-iron  next  to  the  outer  layers  would  impart 
strength  and  toughness  to  the  mass,  and  would  absorb  any 
blows  or  sudden  strains,  which  received  upon  the  outer  surface 
would  encounter  first  a  cushion,  and  then  a  tough  iron ;  and 
that  the  resultant  iron  would  possess  great  power  to  resist  both 
sudden  and  steady  strains,  would  bend  double  without  breaking, 
and,  the  parts  not  being  perfectly  homogeneous,  the  rupture  of 
a  portion  of  a  bar  would  not  render  valueless  the  remainder. 
That  we  secured  all  these  advantages,  our  tests  show  plainly. 

Tested  by  tension,  the  iron  showed  fair  tensile  strength 
(average  53,000  pounds),  uniformity,  and  ductility ;  tested  by 
impact,  bars  of  all  sizes  in  their  normal  condition  would  sustain 
heavy  blows  with  slight  deflection,  and  finally  double  till  the 
sides  were  close  together,  without  injury.  Extreme  tests  were 
made  by  impact :  one  hundred  and  ninety-seven  bars  of  2"  diam- 
eter were  swaged  from  the  blooms,  each  of  which  was  circled 
with  a  score  •£%  °f  an  incn  deep  in  the  centre.  These  bars  were 
struck  upon  this  score  by  the  wedge-shaped  hammer  of  the 
impact  testing  machine,  dropped  from  a  height  of  thirty  feet, 
the  hammer  weighing  one  hundred  pounds.  Each  blow  was 
considered  to  be  equal  to  3,000  foot-pounds. 

2,  or  1  per  cent,  resisted  7  blows. 
5,  or  2.54  per  cent,  resisted  6  blows. 
27,  or  13.6  per  cent,  resisted  5  blows. 
68,  or  34.5  per  cent,  resisted  4  blows. 
71,  or  36  per  cent,  resisted  3  blows. 
21,  or  10  per  cent,  resisted  2  blows. 
3  broke  at  first  blow. 


86  WROUGHT-IRON  AND  CHAIN-CABLES. 

The  three  which  broke  at  single  blow  were  found  to  have 
been  made  partially  of  boiler-steel. 

IRON  A. 

From  these  hammered  blooms,  those  which  had  resisted  at 
least  three  blows  were  re-heated  and  rolled  in  the  copper-mill 
into  iron  A. 

All  the  bars  showed  great  ductility  and  change  of  form  under 
tension,  having  a  rather  low  elastic  limit,  which  was  due,  no 
doubt,  to  the  fact  that  the  softer  and  more  ductile  portions 
stretched  first.  Tested  by  impact,  all  sizes  up  to  2%"  bent  com- 
pletely double  by  heavy  blows  (3,000  foot-pounds)  delivered 
upon  the  centre  of  the  test-pieces,  bending  them  to  the  face  of 
the  wedge,  when  the  steam-hammer  completed  the  closure. 

No  iron  which  we  have  examined  has  proved  superior  to 
this  for  cable-iron;  and  there  is  no  reason  why  any  manu- 
facturer should  not  be  able  to  produce  similar  material,  by 
suitable  mixtures  in  the  piles,  and  by  giving  such  amount  of 
work  as  is  found  to  be  best  adapted  to  develop  good  welding 
properties. 

Even  though  it  should  be  considered  as  impractical  to  arrange 
every  pile  with  due  attention  to  a  balancing  of  opposite  char- 
acteristics, the  quality  of  ordinary  chain-iron  can  be  vastly 
improved  by  subjecting  the  coarse  material  of  which  it  is  gen- 
erally composed  to  much  more  thorough  working  than  is  ordi- 
narily the  custom. 

IRON  B. 

Three  bars  of  this  iron,  viz.,  lyf",  1-JJ"?  and  1TV'>  were  ^lir~ 
nished  as  sample  bars  to  compete  for  an  order  for  chain-iron, 
with  bars  of  irons  C,  E,  G,  H,  I,  J,  K,  and  L,  all  of  which  are 
referred  to  as  the  "  nine  ^irons."  By  the  result  of  the  tests,  this 
iron  was  accepted  for  the  three  sizes,  the  contractor  having  sub- 
stituted samples  of  iron  B  at  the  last  moment  for  those  of  iron 
L  previously  furnished,  which  proved  red-short  and  worthless. 
This  iron  showed  plainly  the  effect  upon  quality  of  increased 
reduction  by  the  rolls,  the  smaller  sizes  being  the  most  ductile 
and  welded  most  firmly. 


NOTES   UPON   THE   IRONS   EXAMINED.  87 

• 

IRON  C. 

Three  bars  of  this  iron,  viz.,  If",  If",  and  li",  were  furnished 
to  compete  with  the  "  nine  irons ; "  and  upon  the  results  of  the 
tests  this  iron  was  received  in  the  above  sizes. 

The  tests  by  tension  and  impact  of  the  sample  bars  showed 
great  ductility,  low  tensile  strength,  and  remarkable  toughness, 
with  great  power  to  resist  impact. 

•As  cable  the  welding  value  was  high,  and  the  single  links 
developed  from  178  per  cent  to  199  per  cent  of  the  bar's 
strength,  averaging  187  per  cent. 

The  iron  delivered  differed  greatly  from  the  samples:  the 
tensile  strength  was  higher ;  and,  although  generally  tough  and 
strong,  the  characteristics  of  the  iron  delivered  showed  that  it 
had  received  much  less  work  than  the  samples,  if  of  the  same 
material.  As  cable  links  the  1J"  developed  an  average  of  162 
per  cent,  the  If"  155  per  cent,  and  the  If"  153  per  cent,  of  the 
bar's  strength,  made  up  of  very  irregular  factors,  ranging  from 
134  to  177  per  cent.  The  If"  was  brittle  under  impact,  the 
If"  less  so,  and  the  li"  generally  very  tough. 

IRON  D. 

Two  lots  of  this  iron,  each  consisting  of  nine  bars  from  2"  to 
1",  were  purchased  for  testing.  Differences  in  the  amount  of 
reduction  in  the  rolls  produced  with  this  iron  very  marked 
differences  in  strength,  —  the  smaller  bars  having  much  greater 
tenacity  than  the  larger  ones.  All  sizes  possessed  great  power 
to  resist  impact,  except  the  2"  bars,  which  were  generally  very 
brittle. 

It  seems  probable  that  the  second  lot,  having  been  prepared 
expressly  for  test,  received  a  great  deal  more  work  than  the 
first.  This  overwork  manifested  itself  both  in  increased  tena- 
city and  in  decreased  welding  value  ;  the  single  links  of  the  first 
lot  developing  an  average  of  178  per  cent,  and  the  sections  of 
the  second  158  per  cent  of  the  bar's  strength. 

The  2"  bar  of  both  lots  differed  greatly  from  all  the  smaller 


88  WROUGHT-IRON  AND   CHAIN-CABLES. 

bars,  —  so  greatly  that  it  was  difficult  to  believe  that  they  were 
of  the  same  iron.  Both  were  very  brittle  under  impact,  and 
when  tested  by  tension,  broke  with  almost  imperceptible  change 
of  form,  showing  bright  granulous  surface  of  fracture. 

IRON  E. 

The  iron  was  all  of  good  quality,  moderate  tensile  strength 
tough  under  impact,  and  made  good  cable. 

This  set  of  bars  presented  one  peculiarity:  the  1£",  instead 
of  being  of  less  tensile  strength  than  the  If",  as  is  generally 
the  case,  was  of  greater ;  and,  on  inquiry  at  the  mill  for  the 
cause,  we  found  that  at  this  mill  the  pile  used  for  the  1£"  was 
of  the  same  sectional  area  as  that  of  the  li",  while  at  most 
mills  it  is  less. 

IRON  F. 

None  of  the  bars  furnished  can  be  considered  as  chain-iron,  for 
which  purpose  the  manufacturers  made  a  harder  and  stronger 
iron.  We,  however,  tested  many  of  them  in  the  form  of  cables, 
considering  that,  in  the  records  of  such  cables,  we  would  find 
what  could  be  expected  of  iron  of  very  low  tensile  strength. 
F  proved  uniform  under  every  form  of  test,  the  tensile  strength, 
elongation,  reduction  of  area,  strength  of  links,  and  percentage 
of  bar's  strength  developed  by  links,  resistance  to  impact,  and 
welding  qualities,  of  any  one  lot,  furnishing  valuable  evidence 
as  to  what  might  be  expected  of  another. 

IRON  Fx. 

The  bars  of  this  iron  were  rolled  from  piles  made  up  of  the 
same  combination  of  crude  irons  as  was  used  in  the  manufac- 
ture of  iron  F,  but  which  piles  were  made  to  differ  from  those 
of  F  in  sectional  area. 

The  proprietors  of  the  rolling-mill  furnished,  without  charge, 
all  the  facilities  and  material  necessary  to  assist  the  committee 
in  an  investigation  into  the  effects  of  the  rolls ;  the  object  of 
the  experiments  being  the  production  of  a  set  of  bars,  of 
various  sizes,  the  tensile  strength  per  square  inch  of  which 
should  be  uniform. 


NOTES   UPON  THE  IKONS   EXAMINED.  89 

This  result  was  accomplished,  on  the  third  trial,  by  so  grad- 
uating the  sectional  areas  of  the  various  piles,  that  the  areas  of 
the  bars  rolled  from  them  bore  uniform  ratios  to  those  of  the 
piles.  (See  the  record  of  this  experiment,  page  18.) 

The  resulting  bars  had  received  much  more  work  than  iron 
F:  they  had  higher  tenacity,  equal  if  not  superior  resilience, 
but  inferior  welding  qualities. 

IRONS  G,  H,  I,  AND  J. 

These  bars  were  furnished  to  compete  with  the  nine  irons  for 
a  contract,  but  few  tests  were  made  upon  them. 

G  and  H  both  proved  of  good  fibrous  material,  sufficiently 
worked,  and  the  few  links  made  from  them  were  strong ;  G,  as 
single  links,  being  equal  to  174  per  cent,  and  H  to  182  per 
cent,  of  the  bar's  strength. 

Iron  I  was  thoroughly  red-short;  and  it  was  impossible  to 
make  links  from  it,  they  breaking  while  being  bent. 

Six  bars  of  iron  J  were  furnished,  which  proved  to  be  of  a 
kind  called  in  the  shop  "rotten."  When  tested  by  impact, 
with  a  sledge-hammer,  the  bars  would  split  tinder  the  blows, 
showing  smooth,  black  faces,  resembling  charcoal. 

IRON  K. 

All  the  bars  of  this  iron  were  of  the  same  character,  which 
was  that  of  a  fine-grained,  thoroughly-worked,  refined  bar,  of 
great  tensile  strength  and  uniformity,  showing,  when  broken 
by  any  form  of  force,  fine  bright  silvery  fractures. 

The  bars  were  so  uniform  in  strength  that  they  were  selected 
as  the  material  from  which  to  make  experiments  which  de- 
pended upon  uniformity  in  character  of  material  for  their 
value.  Under  impact-tests,  iron  K  gave  peculiar  results:  if 
the  skin  was  intact,  a  bar  of  2"  diameter  could  be  doubled, 
cold,  by  heavy  blows,  without  showing  injury ;  but  if  a 
slight  score,  or  nick,  was  made  in  it,  this  power  was  entirely 
lost. 

The  welding  properties  were  not  good,  that  is,  by  the  ordi- 


90  WROUGHT-IRON   AND   CHAIN-CABLES. 

nary  process.  With  some  of  the  links,  that  were  probably 
welded  at  suitable  heat,  the  welds  were  firm,  and  they  pos- 
sessed great  strength ;  but  others,  made  from  the  same  bars, 
broke  at  very  low  strains. 

The  character  of  the  material  was  so  opposite  to  that  of 
charcoal-bloom  boiler-iron,  each  possessing  valuable  qualities 
which  were  lacking  in  the  other,  that  it  was  resolved  to  make 
some  experiments  by  mixing  the  two ;  and  the  results  show 
plainly,  that,  by  such  admixture,  iron  superior  for  chain-cables 
to  either  of  the  constituents  could  be  produced,  and  that  ex- 
cellent chain-iron  can  be  made  by  mills  whose  ordinary  prod- 
ucts cannot  be  considered  as  suitable. 

IRON  L. 

Five  bars  were  furnished  to  compete  with  the  nine  irons. 
All  forms  of  test  indicated  that  the  material  was  steel ;  which 
analyses  subsequently  confirmed.  The  tensile  strength  was 
great ;  reduction  of  area  abrupt ;  power  of  resistance  to  impact 
very  slight  when  scored,  but  fair  when  not  scored;  welding- 
value  low  ;  strength  of  links  very  irregular. 

IRON  M. 

A  great  number  of  tests  were  made  upon  this  iron,  both  by 
physical  and  chemical  processes.  It  was  delivered  as  chain- 
iron  at  a  number  of  different  times  and  lots.  The  bars  of  these 
lots  varied  greatly  among  themselves ;  and  the  lots  differed  in 
many  respects. 

As  cable,  the  iron  proved  very  defective  and  irregular.  The 
trouble  with  it  seemed  to  be,  that,  if  not  welded  at  exactly 
the  right  heat  (a  very  low  one),  the  part  of  the  link  upon 
which  the  weld  was  made  lost  its  strength  by  the  process, 
and  in  many  cases,  when  tested,  the  links  would  break 
through  the  weld  at  very  low  strains,  showing  little  or  no 
change  of  form,  and  the  fractured  ends  remaining  unreduced 
in  diameter. 


NOTES   UPON  THE  IKONS   EXAMINED.  91 

IKON  N. 

The  bars  of  this  iron  (eight  in  number)  were  furnished  to 
the  committee  by  a  leading  manufacturer  as  samples  of  "  first- 
class  chain-iron ;  "  and  they  were  probably  a  fair  sample  of  the 
ordinary  character  of  such  chain-iron:  tested  by  tension,  the 
strength  was  generally  high,  change  of  form  slight. 

Under  impact,  the  large  bars  were  very  brittle,  the  2" 
breaking  by  blows,  when  unscored,  which  the  1§"  resisted  after 
being  scored.  As  cable,  the  If"  was  superior  to  the  2". 

The  fault  with  this  iron  was  too  little  work,  the  large  bars 
receiving  much  less  than  the  small  ones. 

IRON  O. 

This  iron  is  in  no  sense  of  the  word  a  chain-iron ;  and  its 
merits  should  not  be  judged  by  its  action  in  the  form  of  cable. 

The  material  was  soft  charcoal-bloom,  and  of  high  price. 

It  proved  of  value  in  our  experiments  upon  the  effect  of  the 
rolls,  and  as  furnishing  us  with  data  as  to  the  extreme  of 
change  of  form  which  would  occur  to  a  link  of  very  soft  iron 
under  stress.  Although  too  ductile  and  soft  for  chain-iron, 
some  of  the  larger  sizes  produced  good  links,  while  the  smaller 
sizes  were  overworked  for  the  purpose,  and  did  not. 

IKONS  P  AND  Px. 

These  irons  were  made  at  the  same  rolling-mill,  and  when  the 
physical  tests  were  made  upon  Px  it  was  considered  to  be  of 
the  same  material  as  P ;  and  the  differences  in  their  character- 
istics were  attributed  to  variations  in  the  mechanical  processes 
by  which  they  were  produced,  P  having  received  one  course 
of  heating  and  hammering  which  was  omitted  with  Px.  Sub- 
sequently chemical  analyses  showed  marked  differences  in  the 
nature  of  the  two  irons.-  The  results  of  the  analyses  were  con- 
firmed by  a  letter  from  the  manufacturer,  in  which  he  states 
that  he  perceives  that  the  weak  point  of  previous  lots  (iron  P) 
was  the  lack  of  transverse  strength  when  scored,  and  that  he 


92  WKOTJGHT-IBON  AND   CHAIN-CABLES. 

lias  in  this  lot  (Px)  overcome  the  difficulty,  without  essen- 
tially lowering  the  tensile  strength.  This  was  effected  by,  first, 
the  selection  and  rigid  puddling  of  pig-iron  as  free  from  phos- 
phorus as  possible ;  secondly,  using  a  physic,  which  tended  to 
eliminate  the  silicon  and  sulphur;  and  finally,  the  omission 
of  the  hammering.  The  result  of  these  experiments  by  the 
manufacturer,  to  correct  the  defects  found  at  the  testing- 
machine,  was  the  production  of  a  superior  chain-iron,  which 
resisted  impact  well,  and  welded  firmly. 


PART  II.  —  COMPARISON   OF   CHEMICAL  AND  PHYSICAL 

RESULTS. 

Variations  in  the  physical  qualities  of  iron  may  be  due  to 
different  composition,  or  to  different  treatment  in  manufacture, 
or  to  both  of  these  complex  causes.  In  order  to  determine  the 
specific  causes  of  variation,  one  class  of  altering  conditions 
should  be  made  to  vary  largely,  while  the  other  class  should 
be  kept  uniform.  Then  another  class  should  be  varied,  and 
so  on  until  the  value  of  each  is  ascertained.  As  all  the  irons 
under  consideration  were  intended  to  have  that  purity  and 
refinement  which  was  deemed  indispensable  in  chain-cables, 
their  chemical  analyses  are,  perhaps,  more  important  in  proving 
that  physical  variations  result  chiefly  from  variations  in  treat- 
ment, than  in  pointing  out  the  specific  effects  of  certain  in- 
gredients. While  the  subject  of  treatment  —  especially  the 
increase  of  strength  by  greater  reduction  in  rolling  —  may  be 
the  more  important  one,  it  can  best  be  appreciated  after  we 
have  familiarized  ourselves  with  the  general  chemical  and 
physical  characters  of  the  irons.  The  typical  facts  are  given 
in  the  following  tables :  — 


COMPARISON   OF   CHEMICAL  AND   PHYSICAL   RESULTS.      93 


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WKOUGHT-IKON  AND   CHAIN-CABLES. 


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COMPARISON   OF   CHEMICAL  AND   PHYSICAL   RESULTS.       95 


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WROUGHT-IRON  AND   CHAIX-CABLES. 


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COMPAKISON   OF  CHEMICAL  AND   PHYSICAL   RESULTS.      97 

Table  I.  Analyses  of  the  irons. 

Table  II.  Relative  values  of  irons  in  bars,  in  tenacity,  reduc- 
tion of  area,  and  elongation,  and  in  proportion  of  chain  to  bar. 

Table  III.  Summary  of  principal  physical  and  chemical  char- 
acteristics of  sixteen  irons. 

Under  the  head  of  phosphorus,  the  leading  chemical  and 
physical  facts  about  each  iron  likely  to  be  affected  by  this 
element  are  compared,  and  then  the  group  of  irons  is  con- 
sidered, and  a  conclusion  is  reached ;  under  the  head  of  silicon^ 
the  irons  are  again  gone  over  in  a  similar  manner ;  and  so  on 
with  carbon  and  other  ingredients.  A  description  of  a  few 
irons,  in  which  composition  should  have  the  greatest  influence 
on  strength,  will  suffice  to  introduce  these  conclusions. 

EFFECTS  OF  PHOSPHORUS. 

Iron  O :  P.,  O.OT ;  Si.,  0.07 ;  C.,  0.04 ;  slag,  medium. 

Chemical  impurities  all  very  low. 

The  iron  had  been  thoroughly  worked. 

Tenacity  as  bar  and  as  link  very  low. 

Ductility  as  bar  and  as  link  very  high. 
(    Welds  very  good. 

Low  phosphorus  does  not  alone  account  for  these  qualities^ 
Iron  F,  with  P.,0.20,  Si.  0.16,  and  G.  0.03,  has  about  the  same 
tenacity  and  welding  power,  and  approaches  the  same  ductility! 
Iron  P,  with  P.  0.25,-  Si.  0.18,  and  C.  0.083,  has  about  equal 
ductility,  but  inferior  welding  qualities.  Seeing  that  the 
thorough  working  of  the  small  bars  decreased  welding  power, 
as  compared  with  that -of  the  less  compressed  large  bars,  it  is 
probable  that  method  of  manufacture  is  an  important  factor  in 
all  physical  results.  The i  effects  of  low  phosphorus  are  not 
conspicuous. 

IronP:  P.,  0.25 ;  Si.,  0.18 ;  C.,  0.03  ;  slag,  very  low. 

P.,  rather  high  ;  C.,  medium  ;  other  impurities,  low. 

Tenacity  high  as  bar,  irregular  as  link. 

Ductility  high  when  .not  nicked,  low  when  nicked.  Welding 
value  medium,  through  overwork,  andjpossibly  high  P. 


98  WROTJGHT-IKON  AND  CHAIN-CABLES. 

Iron  Px:  P.,  0.09;  Si.,  0.028;  C.,  0.066. 

This  iron  had  the  highest  average  of  good  qualities  of  the 
commercial  bars  examined,  and  was  the  best  for  general  con- 
struction purposes.  The  characteristic  effects  of  phosphorus 
might,  previous  to  our  investigation  into  the  effects  of  reduc- 
tion, have  been  considered  as  shown  by  the  behavior  of  two 
specimens,  one  of  iron  P,  and  one  of  Px,  made  in  the  same  way, 
except  that  one  course  of  piling  and  hammering  was  omitted 
from  Px  ;  viz.,  — 

V  bar-iron  P :  phosphorus,  0.25 ;  tenacity,  57,807  pounds ; 
elongation,  19  per  cent. 

If"  bar-iron,  Px :  phosphorus,  0.09  ;  tenacity,  54,212  pounds ; 
elongation,  24  per  cent. 

But  this  increased  tenacity  and  decreased  ductility  of  the 
smaller  bar  are  not  due  to  P.  alone :  it  had  Si.  0.18  against 
Si.  0.03,  and  it  had  more  reduction  in  the  rolls. 

The  difference  in  the  tenacity  of  the  bars  of  the  same  sizes 
of  iron  P,  which  may  be  considered  as  probably  of  similar 
composition,  was  nearly  5,000  pounds ;  while  between  the  bars 
in  question,  P  and  Px,  it  was  but  3,600  pounds. 

Phosphorus  may  have  affected  the  welding  qualities  and  the 
ductility ;  as  iron  Px,  with  much  less  of  this  element,  welded 
much  better,  and  had  greater  powers  of  resisting  sudden  strains, 
than  iron  P. 

Iron  D:  P.,  0.18  (0.12  to  0.24);  Si.,  0.15;  C.,  0.03-  slag, 
low. 

Carbon  low,  other  impurities  medium. 

Different  bars  very  differently  worked. 

Tenacity  high  as  bar  and  link. 

Ductility  medium  as  bar  and  link. 

"Welds  very  good. 

There  are  various  proofs  that  low  phosphorus,  even  with  low 
silicon,  does  not  cause  high  ductility,  and  that  the  amount  of 
reduction  is  the  more  important  factor.  For  instance :  — 

1"  bar,  P.  0.24,  Si.  0.17,  has  tenacity  per  square  inch,  61,000 
pounds ;  elongation,  26  per  cent. 


COMPARISON  OF  CHEMICAL  AND  PHYSICAL  RESULTS.      99 

li"  bar,  P.  0.16,  Si.  0.11,  has  tenacity  per  sqdare  inch,  56,000 
pounds  ;  elongation,  23  per  cent. 

2"  bar,  P.  0.21,  Si.  0.16,  lias  tenacity  per  square  inch,  49,146 
pounds ;  elongation,  0.07  per  cent. 

The  welds  of  the  medium-sized  and  worked  bars  are  the  best, 
but  all  were  good.  No  harmful  effects  of  phosphorus  can  be 
traced  in  this  iron. 

Iron  B  welded  best,  and 'had  P.  0.23,  and  C.  0.015. 

Iron  F:  P.,  0.20  ;  Si.,  0.16;  C.,  0.03;  slag,  low. 

Carbon  low,  other  impurities  medium. 

Iron  suitably  worked  for  welding,  and  very  uniform. 

Tenacity  as  bar  and  as  link  very  low. 

Ductility  high. 

Welding  power  good. 

The  remarkable  uniformity  of  this  iron  proves  it  to  have 
been  made  with  great  care,  from  selected  materials.  Why  its 
tenacity  is  so  low,  it  is  difficult  to  say,  on  chemical  grounds. 
The  same  iron,  Fx,  more  worked,  gives  a  medium  tenacity,  with 
substantially  the  same  analysis.  Iron  A,  with  less  P.,  Si.,  and 
C.,  is  stronger.  Iron  B  has  lower  P.,  the  same  Si.,  and  only  0.02 
C.,  and  yet  a  higher  tenacity. 

Iron  Fx  (F  more  worked):  P.,  0.19;  Si.,  0.17;  C.,  0.03. 

Ingredients  substantially  the  same  as  in  F. 

Iron  much  more  worked  than  F. 

Tenacity  medium  in  link  and  bar. 

Ductility  good. 

Welding  power  below  medium. 

Iron  B :  P.,  0.23  ;  Si.,  0.16  ;  C.,  0.015. 

P.  rather  high,  Si.  medium,  and  C.  very  low. 

Iron  not  sufficiently  worked  for  strength. 

Tenacity  rather  low. 

Ductility  quite  low. 

Welds  very  good. 

Notwithstanding  the  extremely  low  C.,  the  iron  was  not  duc- 
tile. P.  may  well  account  for  this,  but  not  for  low  tenacity,  as 
some  of  iron  F  had  more  P.,  and  much  higher  tenacity.  Low 


100  AVROUGHT-IBOX  AND   CHAIN-CABLES. 

C.  may  partly  account  for  low  tenacity  and  good  welds,  but 
small  reduction  seems  to  be  an  equal  cause.  High  P.  did  not 
prevent  excellent  welding. 

Iron  M:  P.,  0.25  (0.21  to  0.32)  ;  Si.,  0.18  (0.16  to  0.26)  ;  C., 
0.04;  Ni.,  0.18  (0.03  to  0.34);  Cu.,  0.34  (0.13  to  0.43);  slag, 
various. 

P.  rather  high,  Si.  above  medium,  copper  and  nickel  high-, 
C.  rather  low. 

The  amount  of  work  the  iron  received  can  only  be  inferred 
from  the  sizes  of  the  bars. 

Tenacity  considerably  above  average. 

Ductility  average. 

Welds  weak. 

The  character  of  this  iron  is  so  complex,  and  its  physical 
character  varies  so  much  in  the  same-sized  bars,  that  no  satis- 
factory analysis  of  the  data  can  be  made.  It  seems  certain 
from  a  comparison  of  the  tables,  that  neither  copper,  nickel, 
cobalt,  nor  slag  materially  affected  strength.  The  effects  of 
these  ingredients  on  welding  will  be  considered  under  another 
head.* 

Conclusions  about  Phosphorus.  —  The  best  of  these  irons 
average  P.  0.09  to  0.20.  The  extreme  limits  are  0.065  and 
0.317.  A  soft  boiler-plate- steel  might  have  the  former  amount: 
the  latter  would  give  high  tenacity  and  brittleness  to  even  a 
low  carbon  steel.  The  investigations  have  been  made  so  diffi- 
cult by  the  chemical  similarity  and  general  purity  of  most  of 
the  irons,  and  by  their  various  degrees  of  reduction  in  roll- 
ing, that  the  effects  of  phosphorus  cannot  be  independently 
traced. 

The  phosphorus  (average  in  each  iron)  runs  very  irregularly 
as  follows,  beginning  with  the  highest  of  the  following  physi- 

*  Chromium  occurs  only  in  iron  M,  four  analyses  of-  which  show,  Cr.  0.061  to  0.089.  As  this 
element  is  known  to  increase  the  tenacity  of  steel,  it  may  have  hrought  iron  M  up  to  a  good 
standard  of  tenacity  without  helping  its  other  stuctural  qualities.  These  experiments  give  no 
absolute  evidence  as  to  the  effects  of  chromium ;  but  it  may  be  said  that  when  mere  tenacity  is 
made  the  criterion  of  fitness,  an  iron  like  M  may  be  found  which  will  meet  that  requirement,  and 
still  prove  untrustworthy  for  cables. 


COMPARISON  OF   CHEMICAL  AND  PHYSICAL  RESULTS.       101 

cal  values :  Tenacity,  0.72,  0.15,  0.20,  0.17,  0.22,  '0.25,  0.19,  0.19, 
0.09,  0.15,  0.19,  0.23,  0.18,  0.20,  0.20,  0.07.  Reduction  of  Area, 
0.07,  0.18,  0.09,  0.20,  0.15,  0.25,  0.19,  0.19,  0.20,  0.22,  0.17,  0.15, 
0.23,  0.19,  0.07,  0.20.  Elongation,  0.09,  0.25,  0.07,  0.18,  0.19, 
0.20,  0.19,  0.22,  0.20,  0.19,  0.15,  0.17,  0.15,  0.23;  0.20,  0.07. 

It  may  be  generally  stated  that  phosphorus  0.10,  with  carbon 
about  0.03,  and  silicon  under  0.15,  gave  the  best  chain-cable 
irons  of  this  group.  One  of  the  best  irons,  however,  had  P. 
0.23,  although  low  tenacity  and  high  ductility  are  the  chief 
requirements  of  such  irons. 

The  effects  of  the  different  constituents  on  welding  will  be 
considered  under  that  head. 

EFFECTS  OF  SILICON. 

See  foregoing  description,  of  irons  O,  P,  F,  and  M. 

In  iron  F,  which  is  among  the  highest  in  silicon,  did  this  ele- 
ment cause  the  very  low  tenacity  despite  the  fair  amount  of  P. 
(0.20)  ?  If  so,  Si.  must  affect  tenacity  more  than  it  affects  duc- 
tility. But  this  is  not  the  fact.  In  iron  J,  ductility  as  well  as 
tenacity  is  made  very  low  by  high  Si.  (0.27). 
,1  Iron  J:  Si.,  0.27  (0.18  to  0.32);  P.,  0.20;  C.,  0.035;  slag, 
average. 

Silicon  high,  other  impurities  medium. 

Iron  not  overworked. 

Tenacity  very  low  in  bar  and  link. 

Ductility  very  low  in  bar  and  link. 

Weld  rather  bad. 

There  was  no  apparent  chemical  or  physical  cause  for  this 
low  strength,  except  excessive  silicon.  Under  sledge-blows  the 
bars  split  as  often  as  they  broke  off;  and  the  faces  of  the  fracture 
were  like  layers  of  charcoal,  although  both  carbon  and  slag 
were  medium. 

Conclusions  about  Silicon.  —  No  ingredient  of  steel  is  less 
understood  than  this  one.  The  technical  managers  of  the 
Terrenoire  Works  in  France,  who  have  been  notably  successful 
in  their  steel  manufactures  founded  on  chemical  induction, 


102  WKOUGHT-IRON  AND  CHAIN-CABLES. 

especially  in  the  manufacture  of  sound  steel  castings  which 
contain  a  large  amount  of  Si.,  believe  that  this  ingredient, 
up  to  the  amount  contained  in  most  of  the  irons  we  are  con- 
sidering, does  not  decrease  the  tenacity  or  ductility  of  steel. 
And  it  is  true  that  good  steels  are  made  by  various  processes 
with  as  much  as  0.20  Si.  It  is  believed  by  the  Terrenoire 
managers  that  silica  is  the  cause  of  the  bad  effects  usually 
attributed  to  silicon.  The  table  of  analyses  will  show  that  in 
this  case  the  ore  has  not  been  mistaken  for  the  metal.  The 
slag,  which  contains  the  silica,  has  been  separately  determined. 
Why  wrought-iron  should  differ  from  steel  in  respect  of  the 
effects  of  Si.,  we  have  not  so  far  been  able  to  determine,  if, 
indeed,  it  does  so  differ.  It  can  only  be  said,  with  reference 
to  this  series  of  experiments,  that  there  is  an  apparent  decrease 
of  strength  due  to  an  excess  of  this  element,  while  the  effects 
of  medium  amounts  of  it  are  overshadowed  by  larger  causes. 
The  extremes  of  Si.  were  0.028  and  0.321.  In  the  best  irons 
it  averaged  about  0.15.  It  ran  as  follows,  with  a  regularly 
decreasing  order  of  value :  In  Tenacity,  Si.,  0.09,  0.15,  0.15, 
0.15,  0.18,  0.18,  0.17,  0.16,  0.03,  0.16,  0.16,  0.16,  0.14,  0.27, 
0.16,  0.07.  Reduction  of  Area,  Si.,  0.07,  0.14,  0.03,  0.16,  0.16, 
0.18,  0.16,  0.16,  0.15,  0.18,  0.15,  0.15,  0.16,  0.17,  0.09,  0.27. 
Elongation,  Si.,  0.03,  0.18,  0.07,  0.14,  0.16,  0.16,  0.16,  0.18,  0.15, 
0.17  0.16,  0.15,  0.15,  0.16,  0.27,  0.09. 

EFFECTS  OF  CAKBON. 

See  foregoing  remarks  on  iron  B,  in  which  C.  is  extremely 
low. 

Iron  L:  C.,  average  0.35,  highest  0.51;  P.,  0.10;  Si.,  0.10; 
slag,  low. 

Carbon  very  high,  other  impurities  quite  low. 

Tenacity  as  bar  highest. 

Ductility  as  bar  and  link  lowest. 

Welding  power  most  imperfect,  decreasing  as  C.  increases. 

The  following  table,*  from  a  paper  by  William  Hackney, 

*  Head  before  the  Institution  of  Civil  Engineers,  London,  April,  1875. 


COMPARISON   OF  CHEMICAL  AND  PHYSICAL  RESULTS.        103 

Esq.,  is  valuable  in  this  connection,  as  showing  the  amounts  of 
C.  in  various  well-known  brands  of  wrought  iron  and  steel. 

Percentages  of  Carbon  in  some  Varieties  of  Iron  and  Steel. 


SERIES  OF  THE  IKONS. 

SERIES  OF  THE  STEELS. 

Description. 

Percentage  of 
Carbon. 

Description. 

Percentage  of 
Carbon. 

Trace.* 
0.016  f 
0.033  f 
0.044  t 
0.09  t 
0.10  J 
0.19  t 
(  0.272  f 
/  0.340  f 
0.054  f 
0.087  t 
0.386  f 
0.30  to  0.40  } 
(  traces.f 
I  0.420  f 
0.501  f 
0.55  J 
1.380  f 

Extra  soft  Fagersta  Bessemer 
gteel    

0.085  § 
0.135  || 

0.22  to  0.24  11 

0.31  1 
0.49  J 

j  0.46  * 

0.30  to  0.50 
0.45  to  0.55  t 

0.6* 
0.75* 
1.05  1 
1.18  f 
1.20* 
1.645  1 

Extra  soft  Dowlais  Bessemer 
steel    

Crewe  boiler-plate  steel,  Bes- 

Lowmoor  boiler-plate  .... 
Staffordshire  boiler-plate     .    . 

Locomotive  crank-axles,  Sera- 
ing  Bessemer  steel  .... 
Locomotive     crank-axle,     by 
Vickers,  Sheffield   .... 

Steely  puddled  iron     .... 
Iron  made  by  Catalan  process 
direct  from  the  ore   .... 

Bessemer  spring  steel     .    .    . 
Crucible  steel  : 
For  masons'  tools     .... 
For  chipping  chisels    .    .    . 
Crank-axle  (by  Krupp)    .    . 
Gun  (by  Krupp)      .... 
For  flat  files         ..... 

Puddled  steel  rail    

Hard  puddled  steel      .... 

Forged  Indian  wootz  .... 

Iron  L  is,  therefore,  a  so-called  puddled  steel,  or  more  prop- 
erly a  weld-steel.  Since  its  impurities,  other  than  C.,  are  so 
small,  it  is  impossible  to  avoid  the  conclusion  that  C.  is  the 
cause  of  its  marked  physical  character.  This  is  more  plainly 
shown  by  the  following :  — 

1£  in.  bar,  C.  0.45,  has  nearly  70,000  pounds  tenacity  per  square  inch,  and 

6.5  per  cent  elongation. 
If  in.  bar,  C.  0.51,  has  67,000  pounds  tenacity  per  square  inch,  and  6.5  per 

cent  elongation. 
Ill  and  IJf  in.  bar,  C.  0.21  to  0.25,  have  average  58,000  pounds  tenacity 

per  square  inch,  and  13  per  cent  elongation. 

IronK:  C.,  0.07;  P.,  C.15 ;  Si.,  0.15;  slag,  low. 
C.  slightly  high,  other  impurities  medium. 
Iron  well  worked  and  very  uniform. 
Tenacity  as  bar  and  link  very  high. 


*  A.  Willis. 
§  D.  Forbes. 


t  J.  Percy. 

||  Snelua. 


J  A.  Greiner. 
IT  F.  W.  Webb. 


104  WROUGHT-IKON  AND   CHAIN-CABLES. 

Ductility  below  medium. 

"Welding  power  quite  low. 

The  ductility  was  very  fair  when  the  bar  was  not  nicked. 
The  fracture  was  fine  and  silvery,  like  that  of  low  steel.  These 
facts,  and  the  medium  amounts  of  other  impurities,  point  to  C. 
as  the  hardening  element.  Irons  having  similar  amounts  of 
P.  and  Si.,  and  low  carbon,  like  irons  A  and  C,  have  lower 
tenacity  and  higher  ductility. 

Iron  E:  C.,  0.018;  P.,  0.18;  Si.,  0.16. 

C.  very  low,  other  impurities  medium. 

Tenacity  below  average. 

Ductility  high. 

Welding  power  pretty  good. 

These  phenomena  seem  to  be  connected  with  low  carbon. 

Conclusions  about  Carbon.  —  So  much  is  known  concerning 
the  influence  of  C.  on  both  wrought-iron  and  steel,  that  there 
is  little  danger  of  falling  into  error  about  it.  The  irons  under 
consideration  have  C.  almost  exclusively  low  and  pretty  uni- 
form :  the  exceptional  cases  give  very  marked  physical  results, 
especially  iron  L,  which  is  the  only  one  really  high  in  C.  *  The 
other  irons  ranged  between  0.015  and  0.07.  Carbon  ran  with 
the  following  decreasing  order  of  value  in  Tenacity:  C.  0.35, 
0.068,  0.032,  0.042,  0.044,  0.033,  0.055,  0.032,  0.066,  0.032,  0.032, 
0.015,  0.02,  0.036,  0.026,  0.043.  Reduction  of  Area,  0.043,  0.02, 
0.066,  0.026,  0.032,  0.033,  0.032,  0.032,  0.032,  0.044,  0.042, 
0.068,  0.015,  0.055,  0.35,  0.036.  Elongation,  0.066,  0.033,  0.043, 
0.02,  0.032,  0.026,  0.032,  0.044,  0.032,  0.055,  0.032,  0.042,  0.068, 
0.015,  0.036,  0.35. 

It  seems  thus  easy  to  vary  the  physical  qualities  of  pud- 
dled iron  by  carbon ;  but  whether  or  not  it  is  easy  to  uniformly 
vary  the  carbon  in  puddled  iron,  the  checkered  history  of  the 
"  puddled-steel "  process  will  show.  As  we  shall  observe  far- 
ther on,  for  uses  in  which  the  value  of  an  iron  depends  on  the 
strength  of  the  particular  kind  of  weld  given  to  these  links, 
C.  must  be  under  0.04.  But  for  uses  in  which  the  strength 
of  the  bar  is  the  measure  of  fitness,  C.  may  run  up  to  0.50  or 
more. 


COMPARISON  OF  CHEMICAL  AND  PHYSICAL  RESULTS.        105 

Manganese  is  so  very  low  in  all  these  irons,  that  its  effects 
cannot  be  traced.  It  is  highest  in  one  lot  of  iron  D,  viz.,  0.097  ; 
but  even  this  could  have  little  effect,  in  view  of  the  fact  that 
Mn.  is  often  three  times  as  high  in  very  soft  steels,  and  some- 
times runs  above  one  per  cent  in  low  structural  steels.  Mn. 
seems  to  toughen  steel,  and  to  make  it  cast  sound :  its  harden- 
ing effect  up  to  Mn.  0.20  to  0.30  is  slight. 

Copper  is  very  low  in  all  the  irons,  except  M  (Cu.  0.31  to 
0.43),  which  has  about  the  average  tenacity  and  ductility.  Cu. 
is  next  highest  (Cu.  0.17)  in  iron  A,  which  has  rather  low 
tenacity,  but  very  high  ductility,  on  account  of  its  low  carbon 
(C.  0.02).  These  experiments  furnish  no  evidence  that  copper 
affects  strength.  Its  effect  on  welding  will  be  further  con- 
sidered. 

Nickel  was  only  high  (M.  0.34)  in  some  of  the  bars  of 
iron  M,  but  did  not  appear  to  affect  their  strength.  That 
it  may  have  helped  their  welding  capacity,  is  further  re- 
ferred to. 

Cobalt  was  so  low  (Co.  0.11  maximum)  that  its  effects  on 
strength  could  not  be  traced.  Possibly  copper  may  have  been 
neutralized  by  Ni.  and  Co.  in  its  effect  on  strength,  but  these 
data  are  not  evidence  one  way  or  the  other. 

Sulphur  was  extremely  low  in  all  the  irons,  S.  0.046  being 
the  highest  percentage  in  one  lot  of  iron  M.  So  little  S.  did  not 
affect  welding  power,  as  we  shall  observe  farther  on ;  and  it 
could  hardly  impair  strength,  when  irons  red-short  from  much 
S.  are  usually  strong.  . 

Slag.  —  This  averages  about  one  per  cent.  It  is  lowest  in 
iron  L  (slag  0.38),  and  highest  in  the  2"  bar  of  iron  N  (slag 
2.26).  This  bar  had  51,700  pounds  tenacity,  and  8.7  per  cent 
elongation ;  while  the  1^"  bar  of  iron  N,  with  1.258  slag,  had 
56,000  pounds  tenacity,  and  21.7  per  cent  elongation.  Was 
this  the  result  of  too  little  work  on  the  larger  bar,  or  of  the 
slag  per  se?  Is  the  presence  of  much  slag  merely  an  indi- 
cation of  too  little  work,  —  of  a  loose  structure  resulting  from 
too  little  condensation  of  the  fibres?  Or  does  the  slag,  as  slag, 


106 


WROUGHT-IROX   AND   CHAIX-CABLES. 


or  dirt,  exert  an  independent  weakening  influence  ?     Referring 
to  the  table  of  analyses  we  find :  — 


IRON. 

SIZE. 

SLAG. 

IRON. 

SIZE. 

SLAG. 

L. 

4" 

0.668 

0 

11* 

1.096 

L. 

8" 

0.388 

o 

If" 

0.974 

L. 

IT 

v 

0.192 

p 

1" 

0.848 

L. 
L. 

U 
1^ 

/I 
a 

0.326 
0.308 

p 

D 

If 

r 

1.214 
0.570 

L. 

1J 

\tr 

0.452 

D 

2" 

0.546 

L. 

1 

-1" 

0.376 

It  appears  that  the  smallest  and  most  worked  iron  often  has 
the  most  slag.  It  is  hence  reasonable  to  conclude  that  an  iron 
may  be  dirty  and  yet  thoroughly  condensed ;  and  it  therefore 
seems  probable  that  the  1|"  bar  of  iron  N  was  4,300  pounds 
stronger  than  the  2"  bar,  partly  because  it  had  one  per  cent 
less  slag.  The  1"  bar  of  iron  P  had  nearly  58,000  pounds  tena- 
city;  while  the  If"  bar  of  Px,  with  0.40  more  slag,  had  a  little 
less  than  53,000  pounds  tenacity.  It  is,  however,  impossible  to 
establish  any  close  conclusions  from  these  small  variations  of 
slag.  The  investigation  requires  analyses  of  irons  equally 
worked,  some  of  the  specimens  being  purposely  made  very 

dirty. 

WELDING. 

Before  comparing  the  irons  under  this  head,  it  may  be  well  to 
briefly  consider  the  heretofore  ascertained  facts,  and  the  specu- 
lations which  grow  out  of  them.  The  generally  received  theory 
of  welding  is,  that  it  is  merely  pressing  the  molecules  of  metal 
into  contact,  or  rather  into  such  proximity  as  they  have  in  the 
other  parts  of  the  bar.  Up  to  this  point  there  can  hardly  be 
any  difference  of  opinion,  but  here  uncertainty  begins. 

What  impairs  or  prevents  welding  ?  Is  it  merely  the  inter- 
position of  foreign  substances  between  the  molecules  of  iron 
and  any  other  substance  which  will  enter  into  molecular  rela- 
tions or  vibrations  with  iron?  Is  it  merely  the  mechanical 


COMPARISON   OF   CHEMICAL   AND   PHYSICAL  RESULTS.        107 

preventing  of  contact  between  molecules,  by  the  interposition 
of  such  substances?  This  theory  is  based  on  such  facts  as  the 
following :  — 

1.  Not   only  iron,  but   steel,  has   been   so   perfectly  united 
that  the  seam  could  not  be  discovered,  and  that  the  strength 
was   as   great   as   it  was   at   any  point,  by  accurately  planing 
and  thoroughly  smoothing  and  cleaning  the  surfaces,  binding 
the  two  pieces  together,  subjecting   them  to  a  welding  heat, 
and  pressing  them  together  by  a  very  few  hammer-blows.     But 
when  a  thin  film  of  oxide  of  iron  was  placed  between  similar 
smooth  surfaces,  a  weld  could  not  be  effected. 

2.  Heterogeneous  steel-scrap,  having  a  much  larger  variation 
in  composition  than  these  irons  have,  when  placed  in  a  box 
composed  of  wrought-iron  side  and  end  pieces  laid  together,  is 
(on  a  commercial  scale)  heated  to  the  high  temperature  which 
the  wrought-iron  will  stand,  and  then  rolled  into  bars  which 
are    more    homogeneous    than    ordinary   wrought-iron.      The 
wrought-iron  box  so  settles  together  as  the  heat  increases,  that 
it  nearly  excludes  the  oxidizing  atmosphere  of  the  furnace,  and 
no  film  of  oxide  of  iron  is  interposed  between  the  surfaces.     At 
the  same  time  the  enclosed  and  more- fusible  steel  is  partially 
melted ;  so  that  the  impurities  are  partly  forced  out,  and  partly 
diffused  throughout  the  mass,  by  the  rolling. 

.The  other  theory  is,  that  the  molecular  motions  of  the  iron 
are  changed  by  the  presence  of  certain  impurities,  such  as  cop- 
per and  carbon,  in  such  a  manner  that  welding  cannot  occur  or 
is  greatly  impaired.  In  favor  of  this  theory  it  may  be  claimed 
that,  say,  two  per  cent  of  copper  will  almost  prevent  a  weld ; 
while,  if  the  interposition  theory  were  true,  this  copper  could 
only  weaken  the  weld  two  per  cent,  as  it  could  only  cover  two 
per  cent  of  the  surfaces  of  the  molecules  to  be  united.  It  is 
also  stated  that  one  per  cent  of  carbon  greatly  impairs  welding 
power,  while  the  mere  interposition  of  carbon  should  only 
reduce  it  one  per  cent. 

On  the  other  hand,  it  may  be   claimed  that  in  the  perfect 
welding  due  to  the  fusion  of  cast-iron,  the  interposition  of  ten 


108  WKOUGHT-IKON  AND  CHAIN-CABLES. 

or  even  twenty  per  cent  of  impurities,  such  as  carbon,  silicon, 
and  copper,  does  not  affect  the  strength  of  the  mass  as  much  as 
one  or  two  per  cent  of  carbon  or  copper  affects  the  strength  of 
a  weld  made  at  a  plastic  instead  of  a  fluid  heat.  It  is  also  true 
that  high  tool  steel,  containing  one  and  a  half  per  cent  of  car- 
bon, is  much  stronger  throughout  its  mass,  all  of  which  has 
been  welded  by  fusion,  than  it  would  be  if  it  had  less  carbon. 
Hence  copper  and  carbon  cannot  impair  the  welding  power  of 
iron  in  any  greater  degree  than  by  their  interposition,  provided 
the  welding  has  the  benefit  of  that  perfect  mobility  which  is  due 
to  fusion.  The  similar  effect  of  partial  fusion  of  steel  in  a 
wrought-iron  box  has  already  been  mentioned.  The  inference  is, 
that  imperfect  welding  is  not  the  result  of  a  change  in  molecu- 
lar motions,  due  to  impurities,  but  of  imperfect  mobility  of  the 
mass,  —  of  not  giving  the  molecules  a  chance  to  get  together. 

Should  it  be  suggested  that  the  temperature  of  fusion,  as 
compared  with  that  of  plasticity,  may  so  change  chemical  affini- 
ties as  to  account  for  the  different  degrees  of  welding  power,  it 
may  be  answered  that  the  temperature  of  fusion  in  one  kind  of 
iron  is  lower  than  that  of  plasticity  in  another,  and  that,  as 
the  welding  and  melting  points  of  iron  are  largely  due  to  the 
carbon  they  contain,  such  an  impurity  as  copper,  for  instance, 
ought,  on  this  theory,  to  impair  welding  in  some  cases,  and  not 
to  affect  it  in  others.  This  will  be  further  referred  to. 

The  next  inference  would  be,  that  by  increasing  temperature 
we  chiefly  improve  the  quality  of  welding.  If  temperature  is 
increased  to  fusion,  welding  is  practically  perfect ;  if  to  plas- 
ticity and  mobility  of  surfaces,  welding  should  be  nearly  perfect. 

Then,  how  does  it  sometimes  occur,  that,  the  more  irons  are 
heated,  the  worse  they  weld? 

1.  Not  by  reason  of  mere  temperature ;  for  a  heat  almost  to 
dissociation  will  fuse  wrought-iron  into  a  homogeneous  mass. 

2.  Probably  by  reason  of  oxidation,  which,  in  a  smith's  fire 
especially,  necessarily  increases  as  the  temperature   increases. 
Even  in  a  gas-furnace,  a  very  hot  flame  is  usually  an  oxidizing 
flame.     The  oxide  of  iron  forms  a  dividing  film  between  the 


COMPARISON   OF   CHEMICAL   AND   PHYSICAL  KESTJLTS.       109 

surfaces  to  be  joined ;  while  the  slight  interposition  of  the  same 
oxide,  when  diffused  throughout  the  mass  by  fusion  or  partial 
fusion,  hardly  affects  welding.  It  is  true  that  the  contained 
slag,  or  the  artificial  flux,  becomes  more  fluid  as  the  tempera- 
ture rises,  and  thus  tends  to  wash  away  the  oxide  from  the  sur- 
faces ;  but  inasmuch  as  any  iron,  with  any  welding  flux,  can  be 
oxidized  till  it  scintillates,  the  value  of  a  high  heat  in  liquefy- 
ing the  slag  is  more  than  balanced  by  its  damage  in  burning 
the  iron. 

3.  But  it  still  remains  to  be  explained,  why  some  irons  weld 
at  a  higher  temperature  than  others ;  notably,  why  irons  high 
in  carbon,  or  in  some  other  impurities,  can  only  be  welded 
soundly  by  ordinary  processes  at  low  heats.  It  can  only  be 
said  that  these  impurities,  as  far  as  we  are  aware,  increase  the 
fusibility  of  iron,  and  that  in  an  oxidizing  flame  oxidation  be- 
comes more  excessive  as  the  point  of  fusion  approaches.  Weld- 
ing demands  a  certain  condition  of  plasticity  of  surface :  if  this 
condition  is  not  reached,  welding  fails  for  want  of  contact  due 
to  mobility ;  if  it  is  exceeded,  welding  fails  for  want  of  contact 
due  to  excessive  oxidation.  The  temperature  of  this  certain 
condition  of  plasticity  varies  with  all  the  different  composi- 
tions of  irons.  Hence,  while  it  maybe  true  that  heterogeneous 
irons,  which  have  different  welding-points,  cannot  be  soundly 
welded  to  one  another  in  an  oxidizing  flame,  it  is  not  yet 
proved,  nor  is  it  probable,  that  homogeneous  irons  cannot  be 
welded  together,  whatever  their  composition,  even  in  an  oxi- 
dizing flame.  A  collateral  proof  of  this  is,  that  one  smith  can 
weld  irons  and  steels  which  another  smith  cannot  weld  at  all, 
by  means  of  a  skilful  selection  of  fluxes  and  a  nice  variation 
of  temperatures. 

To  recapitulate  :  It  is  certain  that  perfect  welds  are  made  by 
means  of  perfect  contact  due  to  fusion,  and  that  nearly  perfect 
welds  are  made  by  means  of  such  contact  as  may  be  got  by  par- 
tial fusion  in  a  non-oxidizing  atmosphere  or  by  the  mechanical 
fitting  of  surfaces,  whatever  the  composition  of  the  iron  may  be 
within  all  known  limits.  While  high  temperature  is  thus  the 


110  WROUGHT-IKON  AND   CHAIN-CABLES. 

first  cause  of  that  mobility  which  promotes  welding,  it  is  also 
the  cause,  in  an  oxidizing  atmosphere,  of  that  "  burning  "  which 
injures  both  the  weld  and  the  iron.  Hence,  welding  in  an  oxi- 
dizing atmosphere  must  be  done  at  a  heat  which  gives  a  com- 
promise between  imperfect  contact  due  to  want  of  mobility  on 
the  one  hand,  and  imperfect  contact  due  to  oxidation  on  the 
other  hand.  This  heat  varies  with  each  different  composition 
of  irons.  It  varies  because  these  compositions  change  the 
fusing-points  of  irons,  and  hence  their  points  of  excessive  oxi- 
dation. Hence,  while  ingredients  such  as  carbon,  phosphorus, 
copper,-  &c.,  positively  do  not  prevent  welding  under  fusion,  or 
in  a  non-oxidizing  atmosphere,  it  is  probable  that  they  impair  it 
in  an  oxidizing  atmosphere,  not  directly,  but  only  by  changing 
the  susceptibility  of  the  iron  to  oxidation. 

The  obvious  conclusions  are :  1st,  That  any  wrought-iron, 
of  whatever  ordinary  composition,  may  be  welded  to  itself  in 
an  oxidizing  atmosphere  at  a  certain  temperature,  which  may 
differ  very  largely  from  that  one  which  is  vaguely  known  as 
"a  welding  heat."  2d,  That  in  a  non-oxidizing  atmosphere, 
heterogeneous  irons,  however  impure,  may  be  soundly  welded 
at  indefinitely  high  temperatures. 

These  speculations  may  throw  little  light  on  the  subject  of 
welding.  They  are  introduced  for  the  purpose  of  indicating 
the  direction  of  further  inquiry  and  experiment,  and  of  im- 
pressing the  necessity  of  caution  in  arriving  at  conclusions 
about  these  irons  from  the  limited  data  afforded  by  these 
experiments. 

In  reviewing  the  experiments  with  reference  to  welding,  and 
under  the  precaution  mentioned,  let  us  observe :  — 

1st,  All  the  irons  were  so  very  low  in  sulphur,  that  this 
ingredient  could  not  have  materially  affected  welding  power. 

2d,  As  we  shall  see  in  detail,  farther  on,  the  irregular  dif- 
ferences in  the  working  and  reduction  of  the  bars,  which 
affected  all  other  physical  properties,  affected  this  one  also. 

Let  us  first  take  the  singularly  impure  iron  M.  Its  surfaces 
were  pretty  well  united  by  welding,  but  the  iron  about  the 


COMPARISON  OF   CHEMICAL  AND   PHYSICAL  EESULTS.        Ill 

weld  was  weakened,  especially  at  a  high  heat.  Of  124  rup- 
tures of  links  made  of  this  iron,  79  were  through  the  weld, 
and  the  iron  was  little  distorted.  Of  311  ruptures  of  links 
made  of  other  irons,  but  37  were  through  the  weld. 

The  li"  bar  of  iron  M  presents  an  exception:  it  stands 
high  on  the  list  in  welding  capacity,  and  contains  copper  0.31 
(average  Cu.  in  iron  M,  0.34).  Its  phosphorus,  slag,  and 
silicon  are  about  average.  But  the  bar  is  also  remarkable  in 
containing  nickel  0.35,  and  cobalt  0.11.  Did  these  ingredients 
neutralize  the  copper  under  this  special  treatment  ?  No  other 
irons  contain  any  notable  amount  of  them,  except  iron  A, 
which  has  Co.  0.07,  and  Ni.  0.08;  but  it  also  has  Cu.  0.17.* 
The  welds  of  this  iron  were  very  strong,  the  links  breaking 
oftener  at  the  butt  than  at  the  weld. 

Two  links  made  from  iron  M  were  analyzed  from  specimens 
taken  at  the  weld  end  and  at  the  butt  end.  •  The  weld  end 
had  been  re-heated  and  hammered  twice;  the  butt  end  had 
not  been  hammered,  and  had  received  second  heat  only  by 
conduction  from  the  other  end.  The  analyses  show  that  silicon 
and  slag  only  were  materially  affected  by  twice  heating  and 
hammering,  as  follows :  — 


SILICON. 

SLAG. 

Iron  M, 

l.i 

>  in. 

bar,  weld  end  ...... 

0.182 

0.998 

(i 

li 

in. 

bar,  butt  end    

0.203 

1.074 

« 

It 

-  in. 

bar,  weld  end  

0.177 

1.388 

ii 

If 

-in. 

bar,  butt  end    

0.261 

1.732 

In  oxidizing  to  silica,  the  Si.  diffused  a  small  amount  of  flux, 
which  should  have  helped  welding  by  preventing  oxidation,  or 
by  carrying  off  oxide  of  iron,  or  both ;  but  the  amount  was  so 
very  small  in  this  case  that  its  effect  cannot  be  traced.  Nor 
does  iron  J,  in  which  Si.  was  highest  (0.18  to  0.32),  confirm 

*  This  iron  may  have  received  the  copper  while  heing  rolled  in  a  train  ordinarily  used  for 
copper,  at  the  Navy  Yard,  Washington,  D.C.,  where  it  was  manufactured. 


112  WEOUGHT-IRON  AND   CHAIX-CABLES. 

this  theory.  Although  the  other  impurities  were  not  high,  and 
the  iron  was  not  overworked,  it  welded  rather  badly.  The 
value  of  short  chains  is  as  follows :  Best,  Si.  0.16,  0.14,  0.07, 
0.03,  0.16,  0.15,  0.17,  0.15,  0.17,  0.18,  0.16,  0.18,  0.15,  and, 
including  J,  0.27. 

Phosphorus,  up  to  the  limit  of  i  per  cent,  had  not  a  notable 
effect  on  welding.  It  was  lowest  in  iron  O,  which  welded 
soundly ;  but  all  impurities  were  low,  and  welding  power  was 
traced  to  the  reduction  of  the  bar  by  direct  experiment.  The 
same  is  true  of  iron  P.  Omitting  one  course  of  piling  and 
hammering  largely  helped  its  welding  power.  Iron  P  welded 
badly,  not  necessarily  on  account  of  its  P.  0.25 ;  for  iron  B, 
with  P.  0.23,  and  iron  D,  with  P.  0.18,  welded  soundly.  Iron 
M  had  the  high  P.  0.23  (0.21  to  0.32).  While  its  surfaces 
stuck  together  pretty  well,  the  links  broke  through  the  weld 
when  they  were  made  at  a  high  heat,  which  may  be  accounted 
for  by  the  fact  that  phosphorus  increases  fluidity,  and  hence 
capacity  for  oxidation.  The  value  of  short  chains  is  in  the 
following  order:  Best,  P.  0.23,  0.18,  0.07,  0.09,  0.20,  0.20,  0.19, 
0.17,  0.19,  0.25,  0.19,  0.22,  0.15. 

Carbon  notably  affected  welding.  It  ran  as  follows  in  con- 
nection with  regularly  decreasing  welding  power:  Best,  C. 
0.015,  0.02,  0.043,  0.066,  0.026,  0.032,  0.032,  0.042,  0.055,  0.033, 
0.032,  0.044,  0.068,  and  including  L,  0.351. 

The  weld  steel,  or  steely  iron,  L  (C.  0.35),  when  treated  by 
the  uniform  method  usually  adopted  for  chain-cable  irons,  made 
the  worst  welds.  Iron  K,  with  carbon  so  low  as  0.07,  made 
bad  welds,  although  it  was  otherwise  a  good  average  chain- 
iron,  with  a  medium  amount  of  impurity.  Carbon,  in  a  greater 
degree  than  phosphorus,  promotes  fluidity:  hence  the  iron  is 
"  burned  "  at  the  ordinary  welding  temperatures  of  low-carbon 
irons. 

Slag  was  highest  (2.26  per  cent)  in  the  'two-inch  bar  of  iron 
N,  which  welded  less  soundly  than  any  other  bar  of  the  same 
iron,  and  below  average  as  compared  with  the  other  irons. 
Slag  should  theoretically  improve  welding,  like  any  flux, 


COMPARISON  OF   CHEMICAL   AND   PHYSICAL  RESULTS.  ,     113 

but  its  effects  in  these   experiments  could  not  be  definitely 
traced. 

WHAT  is  LEARNED  FROM  CHEMICAL  ANALYSES. 

So  far,  it  may  appear  that  little  of  use  to  the  makers  or 
the  users  of  wrought-iron  has  been  learned.  But  it  should  be 
remembered  that  all  these  irons  were  intended  to  be  as  nearly 
as  possible  alike,  and  to  be  adapted  to  the  peculiar  use  of  chain- 
cable.  The  makers  generally  understood  the  necessary  condi- 
tions, and  every  effort  was  made  to  reach  this  special  standard 
of  excellence.  Had  it  been  reached,  the  irons  would  have  all 
been  exactly  alike  in  physical  character,  and  presumably  similar, 
although  not  necessarily  alike,  in  chemical  character,  for  certain 
ingredients  may  replace  others  within  limits  which  are  perhaps 
narrow.  Certainly  the  attempt  to  make  all  the  irons  conform 
to  a  well-known  standard  of  quality  was  the  worst  possible 
way  to  ascertain  the  distinctive  effects  of  the  various  altering 
ingredients.  In  order  to  make  this  latter  determination,  one 
series  of  irons  should  have  been  made  as  uniform  as  possible  in 
all  ingredients  except  one,  for  instance,  phosphorus,  and  that 
one  should  have  been  varied  as  much  as  possible.  Another 
series  should  have  been  alike  except  in  silicon;  and  so  on, 
through  the  list  of  altering  ingredients.  The  series  of  tests 
which  the  Board  has  undertaken  on  steels  was  devised  upon 
this  principle.  It  was,  however,  thought  best,  after  the  physi- 
cal tests  of  these  irons  were  completed,  to  subject  them  to 
analysis,  in  the  hope  that  some  good  result  would  follow.  This 
hope  has  been  realized  in  an  unexpected  and  somewhat  sur- 
prising manner. 

1st,  The  want  of  uniformity  in  the  chemical  composition  of 
the  same  brand  of  iron  is  a  conspicuous  defect  which  is  readily 
accounted  for.  In  iron  M,  silicon  varied  from  0.16  to  0.26; 
in  iron  J,  it  varied  from  0.18  to  0.32.  In  iron  D,  phosphorus 
varied  from  0.12  to  0.24 ;  and  in  iron  J,  from  0.14  to  0.29. 

Starting  with  a  uniform  pig-iron,  the  puddling  process  may 
or  may  not  remove  a  large  amount  of  silicon,  phosphorus,  and 


114  WROUGHT-IRON   AND   CHAIN-CABLES. 

carbon,  according  to  the  temperature  and  agitation  of  the  bath, 
the  "fix"  used  in  the  furnace,  and  from  many  causes  under  the 
puddler's  control,  and  dependent  on  his  knowledge  and  skill. 

Such  variations  would  be  entirely  inadmissible  in  the  most 
common  grades  of  steel :  in  fact,  they  could  not  occur  in  the 
cheap  steel  processes,  when  using  a  uniform  pig-iron,  except  by 
a  special  effort.  In  the  Bessemer  process,  the  completion  of 
the  oxidation  of  silicon  and  carbon  is  obvious  to  the  inexpert 
observer;  in  the  open-hearth  process,  unmistakable  tests  are 
taken  during  the  operation.  The  character  of  steel  can  be 
surely  predicated  on  the  analysis  of  its  materials;  that  of 
wrought-irori  is  altered  by  subtle  and  unobserved  causes. 
Should  it  be  urged  in  favor  of  wrought-iron,  that  P.  can  be 
largely  removed  during  its  manufacture,  while  in  the  steel- 
manufacture  it  cannot  be,  it  may  be  answered  that  there  is  an 
abundance  of  pig-irons  which  do  not  contain  much  P. ;  and  it  is 
better  to  be  sure  of  a  definite  amount  of  a  deleterious  ingre- 
dient than  to  run  the  risk  of  a  variable  amount. 

We  are  not  prepared  to  show  the  exact  effect  of  varying 
reduction  on  steel.  Ingots  of  the  same  grade  of  steel,  from  six 
inches  square  to  fourteen  inches  square,  are  employed  for  the 
same-sized  bars ;  the  larger  ones  are  preferred,  notwithstanding 
the  greater  cost  of  working  them,  not  because  small  ingots  will 
not  make  good  bars :  but  because  they  make  too  much  scrap. 
Steel  depends  comparatively  slightly  on  condensation  for  its 
density,  but  very  greatly  on  its  being  cast  from  a  fluid  state. 
It  is  a  crystalline  mass  in  both  large  and  small  ingots,  and  not 
a  bundle  of  fibres  of  iron  more  or  less  compacted. 

2d,  This  matter  of  varying  strength  due  to  varying  reduction 

—  the  most  important  developed  by  the  series  of  experiments 

—  is  made  all  the  more  certain  and  useful  by  the  analyses ;  for, 
without  a  knowledge  of  the  composition  of  the  bars  and  of  the 
specific  effects  of  different  ingredients,  a  part  of  the  variation 
now  traced  to  reduction  might  have  been  attributed  to  com- 
position. 

It  may  be  stated  in  general  terms,  that,  notwithstanding  this 


COMPARISON  OF   CHEMICAL  AND  PHYSICAL  EESULTS.        115 

• 

attempt  at  uniformity,  the  differences  in  reduction  in  the  roll- 
ing-mill from  pile  to  bar  caused  as  much  variation  in  the 
physical  qualities  of  these  irons  as  did  the  differences  in  the 
chemical  composition  of  the  whole  series  of  irons,  excepting 
the  steely  iron  L.  The  highest  difference  in  tenacity,  due 
apparently  to  varying  reductions,  is  11,969  pounds  per  square 
inch.  The  highest  Difference  between  the  average  tensional 
resistances  of  all  the  irons  (excepting  the  steely  iron  L),  due 
to  all  causes,  is  but  7,109  pounds.  The  following  illustrations 
are  more  in  detail :  — 

Iron  P. 

Per  Sq.  In. 

Tenacity  of  1  in.  bar  (1.74  per  cent  of  pile)  above  2  in.  (6.98  per  cent  of  pile)  .  .  6,973  Ibs. 
Elastic  limit  "  "  "  "  "  "  7,352  Ibs. 

Iron  F.    Second  Lot. 

Tenacity  of  l\  in.  bar  (2.76  per  cent  of  pile)  over  2  in.  (5.23  per  cent  of  pile)  .  .  4,698  Ibs. 
Elastic  limit  "  "  "  "  "  "  3,227  Ibs. 

Iron  F.     Third  Lot. 

Tenacity  of  |  in.  bar  (1.60  per  cent  of  pile)  over  2\  in.  (6.13  per  cent  of  pile)  .        .      9,656  Ibs. 

"             |  in.  bar  (3.68  per  cent  of  pile)  over  4  in.  (15.70  per  cent  of  pile)  .        .      7,786  Ibs. 

Elastic  limit  of  g  in.  bar    "                   "                   "                  "                   "  15,045  Ibs. 

-Tenacity  of  1  in.  bar  (3.14  per  cent  of  pile)         "                 "                  "  4,806  Ibs. 

Iron  N. 
Tenacity  of  1|  in.  bar  (6.62  per  cent  of  pile)  above  2  in.  (11.36  per  cent  of  pile) .        .      4,395  Ibs. 

Iron  A. 

Tenacity  of  1  in.  bar  (3.14  per  cent  of  pile)  over  2  in.  (8.72  per  cent  of  pile)       .        .      4,519  Ibs. 

Iron  D. 

Difference  in  phosphorus  in  1  in.  and  2  in.  bars,  0.026;  other  ingredients  about  alike. 
Tenacity  of  1  in.  bar  over  2  in.  bar 11,969  Ibs. 

The  following  are  apparently  results  of  composition :  — 

Comparative  Tenacity. 

Of  iron  highest  in  average  qualities  over  the  one  lowest  in  impurities  ....  3,136  Ibs. 
Of  most  tenacious  steely  iron  (carbon  0.35)  over  least  tenacious  (carbon  0.04)  .  .  15,464  Ibs. 

3d,  The  variation  of  welding  power  by  reduction,  in  a 
greater  degfee  than  by  composition,  has  already  been  shown  in 
detail.  Chemical  analyses  were  necessary  to  establish  this  fact. 

4th,  To  the  steel  maker  and  user  it  will  appear  somewhat 
remarkable,  that  phosphorus  may  run  up  to  nearly  a  quarter  of 
one  per  cent  in  good  chain-cable  irons,  when  it  is  considered 


116  WROUGHT-IRON  AND   CHAIN-CABLES. 

that  low  tenacity  and  high  ductility  are  the  essential  features 
of  such  irons,  and  that  the  effect  of  this  ingredient  is  to  pro- 
duce exactly  opposite  results.  Suitable  working  probably 
counterbalanced  its  effects. 

5th,  The  comparison  of  chemical  and  physical  results  sug- 
gests a  number  of  experiments  which  would  go  far  to  settle 
vexed  questions,  and  improve  the  practice,  especially  with 
regard  to  welding. 

(1)  Regarding  slag,  it  has  been  shown  that  a  larger  amount 
is  sometimes  found  in  a  well-worked  than  in  a  less-reduced  iron, 
and  that  its   effects   are   uncertain.     Experiments   should   be 
arranged  to  show  what  composition  of  slags  mil  readily  come 
out  of  the  pile  in  rolling ;  whether  two-high  or  three-high  trains 
will  best  remove  them,  and  how  much  and  what  kind  of  slag 
affects  strength  and  welding.     A  stable  oxide  of  iron,  which 
would  probably  do  the  most  harm,  could  be  formed  by  blowing- 
superheated  steam  upon  red-hot  bars  before  piling.     It  might 
be  proved  that  very  fusible  slags,  or  fluxes,  should  be  placed  in 
the  pile  to  protect  surfaces  from  oxidation,  and  to  wash  away 
less  fusible  impurities. 

(2)  It  has  already  been  suggested  that  special  irons,  having 
respectively  a  certain  ingredient  in  excess  and  the  others  low 
and  uniform,  should  be  made,  in  order  to  ascertain,  in  a  con- 
spicuous manner,  the  physical  effects  of  the  various  ingredients. 

(3)  Referring   to   a  previous  recapitulation  of  remarks  on 
welding :  The  effects  of  very  different  temperatures  on  irons 
varying  in  composition,  as  compared  with  that  uniformly  high 
temperature  usually  known  as  a  "  welding  heat,"  should  be 
much  more  carefully  ascertained.     And  the  effects,  and  more 
especially  the  means  of  welding  in  a  non-oxidizing  flame,  where 
mobility  of  surfaces  can  be  got  without  "  burning,"  should  be 
made   the   subject  of    elaborate   experiments.     Tlfe   excellent 
welding  of  a  heterogeneous  mass  of  steel  and  iron,  protected 
from  oxidation  by  being  placed  in  an  iron  box  which  will  stand 
a  high  heat,  has  been  referred  to.     The  system  of  gas-welding 
by  which   Mr.  Bertram  welded  boilers  at  Woolwich  twenty 


COMPAEISON   OF   CHEMICAL   AND   PHYSICAL  RESULTS.        117 

years  ago  has  since  been  in  regular  use  by  the  Butterly  Com- 
pany, in  England,  for  joining  the  members  of  wrought-iron 
beams  of  large  section.  It  should  seem  within  the  power  of 
modern  engineering  and  chemistry  to  provide  means  for  the 
perfection  in  a  non-oxidizing  atmosphere,  of  welds,  like  those 
of  ships'  cables  and  bridge-links,  upon  which  hang  so  many 
lives  and  so  much  treasure. 

<r 

CONCLUSIONS  DERIVED  FROM  A  COMPARISON  OF  CHEMICAL 
AND  PHYSICAL  RESULTS. 

I.  Although  most  of  the  irons  under  consideration  are  much 
'alike  in  composition,  the  hardening  effects  of  phosphorus  and 

silicon  can  be  traced,  and  that  of  carbon  is  very  obvious.  Phos- 
phorus up  to  0.10  per  cent  does  not  harm,  and  probably  im- 
proves, irons  containing  silicon  not  above  0.15,  and  carbon  not 
above  0.03.  None  of  the  ingredients  except  carbon  in  the  pro- 
portions present  seem  to  very  notably  affect  welding  by  ordi- 
nary methods. 

II.  The  strength  of  wrought-iron  and  its  welding  power  by 
ordinary  methods  are  varied  more  by  the  amount  of  its  reduc- 
tion in  rolling  than  by  its  ordinary  differences  in  composition. 
Uniform  strength  may  be  promoted  by  uniform  reduction,  but 
only  at  such  increased  cost  of  manufacture  that  the  practice  is 
not  likely  to  obtain.     Therefore  the  reduced  strength  of  large 
bars  made  by  ordinary  methods  should  be  considered  in  design- 
ing machinery  and  structures. 

III.  In  accordance  with  these  facts  the  United-States  Test 
Board  has  shown,  by  trial,  the  unsafety  of  the  Admiralty  proof- 
tables  for  chain-cable,  and  has  prepared  new  ones,  and  also  new 
tables  of  the  strength  of  different-sized  bars.     The  Board  has 
demonstrated  that  the  tenacity  of  two-inch  bar  for  chain-cable 
should  be  between  48,000  and  52,000  pounds  per  square  inch, 
and  of  one-inch  bar  between  53,000  and  57,000  pounds;  and 
that  stronger  irons  than  these  make  worse  cables,  because  they 
have  low  ductility  and  welding  power. 

IV.  Chemical   analyses,  made   in   connection  with   physical 


118  DROUGHT-IRON:  AND  CHAIX-CABLES. 

tests,  are  indispensable  to  conclusions  about  either  the  charac- 
ter or  treatment  of  iron.  In  this  series  of  experiments  the 
demonstration  that  strength  is  dependent  on  reduction  is  made 
more  definite  and  useful  by  the  analyses. 

V.  Analyses  also  prove  that  the  same  brand  of  wrought-iron 
may  be  heterogeneous  in  composition ;  and  they  emphasize  the 
previously  known  fact  that  wrought-iron  making  processes,  as 
compared  with  the   cheap  steel  processes,  necessarily  give  an 
uncertain  character  to  the  former  material,  while  to  the  latter 
the  desired  quality  may  be  imparted  with  certainty  and  uni- 
formity. 

VI.  The  ordinary  practice  of  welding  is  capable  of  radical 
improvement :  the  fact  has  been  fully  demonstrated;  the  means 
should  be  made  the  subject  of  complete  experiments.     The  per- 
fection of  means  for  welding  in  a  non-oxidizing  atmosphere 
would  seem  to  be  the  promising  direction  of  improvement. 

In  submitting  the  foregoing  history  of  their  experiments,  and 
deductions  therefrom,  the  committees  recognize  the  fact  that 
much  still  remains  to  be  done  before  either  of  the  investigations 
can  be  considered  complete.  But,  having  exhausted  the  time 
and  means  at  their  disposal,  they  are  compelled  to  submit  the 
results  as  far  as  accomplished. 

L.   A.   BEARDSLEE, 

Commander  U.S.N.,  Chairman  of  Committees  D,  //,  and  M. 

Q.   A.    GILLMORE, 

Lieut.-CoL,  Corps  of  Engineers,  Brev.  Major-Gen.,  U.S.A.,  Chair- 
man of  Committee  B,  Member  of  Committee  D. 

A.   L.    HOLLEY,   C.E.,  LL.D., 
Chairman  of  Committee  C,  Member  of  Committee  H. 

WM.    SOOY   SMITH,   C.E., 
Chairman  of  Committees  E  and  K,  Member  of  Committees  H  and  M. 

DAVID   SMITH, 

Chief  Engineer    U.S.N.,   Chairman  of  Committee   0,  Member  of 
Committees  D  and  M. 


NOTE  BY   THE   ABKIDGER.  119 

[NOTE  BY  THE  ABEIDGER.]  The  committees  referred  to 
in  the  signatures  above  were  charged  with  the  following  divis- 
ions of  the  general  work  of  the  Board  :  — 


j 


D.  On  chains  and  wire  rope. 

H.  On  iron,  malleable.  [-  The  committees  making  this  report. 

M.  On  re-heating  and  re-rolling. 

B.  On  armor-plate. 

C.  On  chemical  research.  !  The  reports  of  these  committees 

E.  On  corrosion  of  metals.  I  have  not  yet  been  published. 
K.  On  orthogonal  simultaneous  strains. 


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